Inside the Frantic Search for Tech Billionaires’ Missing Child, Mint Butterfield

Grace Kahng is an Emmy, Peabody, and Amnesty International award-winning investigative journalist with expertise in human trafficking and hunting serial killers. The following is a behind-the-scenes account of the 53 hours leading to the rescue of 16-year-old Mint Butterfield after Kahng was hired and paid by their family to assist in their recovery.

Mint comes from the closest thing tech has to royalty. Mint, who identifies as non-binary and who used they/them pronouns, is the only child of a divorced Silicon Valley power couple, Caterina Fake (the co-founder of Flickr) and billionaire Stewart Butterfield (the co-founder of Slack). Mint has also been raised by Fake’s partner, Jyri Engeström (co-founder of mobile social network Jaiku), with whom Fake has been in a relationship with since Mint was 3.

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The teenager’s disappearance sparked massive publicity after Mint was reported missing on April 22. Their family was initially frantic that the Marin County Sheriff’s Office was spending more time investigating Mint than locating Mint’s alleged abductor, Christopher “Kio” Dizefalo. This is the exclusive story of the search for Mint, their return—and how Dizefalo and a woman named Sarah Atkins ultimately faced charges in connection with Mint’s disappearance.

Mint’s house, Bolinas, California

8:36 a.m., Monday, April 22

Caterina Fake opens the door to bring her child Mint a glass of juice, but the bed is empty. Fake is now living every mother’s nightmare. Mint has vanished from their weekend home in Bolinas, California, a remote coastal town northwest of San Francisco. Bolinas has more cows than people. There is one road in and one road out.

Fake immediately thinks the worst. “I’m terrified. I think, ‘My kid’s been taken.’ It is any mother’s nightmare that their kid is taken—taken from them by somebody that they don’t know.”

Her neighbors help with an impromptu search that yields nothing. Later, Caterina finds a note addressed to her from Mint, telling their mom that they love her.

Caterina brought Mint to this tiny town to escape “Kio”—a 26-year-old man with a tattoo of a scythe on his face—because of an alarming change she witnessed in Mint after meeting him.

Staring at the empty bed, terror strikes her. She feels she knows one thing: Kio has Mint. Panicked Fake dials 911. She thinks: “Will I ever see Mint alive again?”

Alaska Airlines Terminal 2, San Francisco International Airport

8:30 p.m., Thursday, April 25

I’ve been away for nine days investigating the Moby Dick of serial killers: an elderly man who I believe to be responsible for the unsolved 1970s “Santa Rosa Hitchhiker” killings. Solving decades-old cold cases is painstaking work and I’m exhausted. I just want my dog and my bed. As the plane touches down, a flurry of texts asking me to help FIND MINT blows up my phone.

I deal with pimps, johns, lost girls, dead girls, and serial killers. As an investigative journalist with 30 years in the trenches exposing human trafficking and hunting murderers, “Sociopaths R Us” is my motto.

“Hey Grace, there’s a 36-year-old cold case in Lake County, do you want to see if it’s one of your guys?”

“Hey Grace, I have a friend who thinks her freshman daughter is being sold by her boyfriend. Can you help?”

This is a very specific set of skills that either fascinates or repels. My tribe: social workers and cops and nurses and first responders. We joke that we are the garbage collectors of human folly. We get up every day and hope that what we do can make a difference.

Mothers ask for help extracting their daughters from Romeo pimps—sex traffickers who operate by trying to make young girls or boys fall in love with them.

SFO Airport Parking Garage, Level 4

9:42 p.m., Thursday April 25

A light rain is falling, and my smart car is at 7 percent battery. Before I get to Mint’s home I call insiders I trust. “It’s a shit show, Grace, don’t get involved. These people have hired a bunch of goons, PIs, and who-knows-what running around messing things up for patrol on the ground. It’s not going to end well.” Yikes. “The parents have stopped cooperating with the cops,” I’m told. “It’s adversarial.” These are not parents who are going to sit on their hands and wait for help. After founding Flickr and then Slack, Mint’s mom and dad were regulars on Fortune’s Most Powerful tech list.

No doubt, one of the difficulties in a crisis like this is every titan of tech— including Marc Benioff (whose company Salesforce bought Slack for $27 billion in 2021) and Mark Pincus of Zynga—is offering to help and lend manpower. The number of boots on the ground can be counterproductive.

The Palo Alto mommy mafia has coughed up my name and given it to Mint’s mom. On my way home to grab my dog Archie, I call Caterina and agree to meet for 15 minutes. The only thing I know about Mint’s case emanates from tabloids screaming: BILLIONAIRE’S DAUGHTER MISSING.

That must be hard enough for Mint’s parents. In fact, they want to know why the Marin County Sheriff’s Office is leaking what they claim is sensitive, inaccurate information about a minor to the press that they feel simply further endangers her.

“Marin called the press before they even called me back,” says a clearly frantic Fake. “I gave them Kio’s phone number. Instead of going to find him they’re giving interviews to People, the San Francisco Chronicle and New York Post.” Sgt. Adam Schermerhorn, a public information officer with the Marin County Sheriff's Office, said that authorities were “still actively investigating leads and working with the juvenile's mother to try and acquire digital devices and other items that could have information.” The authorities “do not have any reason to believe there is foul play,” or “anything criminal” in connection to Mint’s disappearance, he added.

Every year 800,000 kids go missing and most are taken by men, whether they are family members or strangers. When a child turns up dead, most have been killed within the first 24 hours. This statistic is seared into every mother’s brain, which is why every second counts.

The Marin County Sheriff’s Office initially classifies Mint as “voluntarily missing.” “At this time, we have no information to believe that Mint was taken against their will,” the Sheriff’s Office said in a statement, adding it was “considering Mint a voluntary-missing juvenile, who is ‘at risk’ due to a reported previous threat of suicide.”

Caterina wanted to know: “Why are the cops saying my child is voluntarily missing? Why are they doing that?”

I’m guessing it’s inexperience. Marin County is one of the wealthiest enclaves in the Bay Area. The standard protocol for child trafficking and endangered runaways is to get the victim’s picture out and help Mom make public pleas for information in the press.

My feeling is additional clickbait and hoopla is a distraction and will increase the risk of Mint of being kidnapped for ransom.

At this point of Mint’s disappearance, something has gone awry. Based on what I am told by Mint’s exasperated family, it seems some officers in Marin County are investigating the family instead of looking for Mint.

​​The purpose of this narrative seems to be to blame the victim if something bad transpires. I’m worried Mint is going to be dead in 48 hours, or that they could simply go permanently missing, or be in another kind of serious peril.

Mint’s house, San Francisco

10:38 p.m., Thursday, April 25

I pull up to Caterina’s house and walk inside. This is NOT a billionaire’s house. Not even close. I have been in billionaires’ homes. Clue #1: There’s no “staff.” Instead, I am greeted by two small scruffy, barking rescue dogs. One of them is being held by Caterina. She looks at my dog Archie, and says “Another small dog person. That’s a good sign.” I smile because I am thinking the same thing.

I also notice Caterina looks Asian. “I’m Korean,” I tell her. “I’m half Filipino,” she replies. “Which half?” I ask. “My mother.” Women with Asian mothers belong to an exclusive club.

Where’s Mint’s dad? “I’m basically a single mom,” she says. (Mint’s stepdad, Jyri, commutes from Finland; it’s a long-distance relationship.) I look at Caterina and see a mom who fiercely loves her child. A mom who has spent every waking hour of her life loving her child. Maybe too much. A mom pushed to the brink of madness. I said I would stay 15 minutes. I stayed six hours.

Some history: In July 2023, Mint turned 16 and started going to punk and emo clubs in the East Bay to listen to music. Mint is brilliant, insatiably curious, and sweet. During their formative years they were homeschooled and COVID hit. The isolation, disruption, and panic of the pandemic had a decidedly negative impact on Mint’s development along with that of 43 million other American teens.

I spoke to friends of Mint’s whose parents asked she remain anonymous, who was with Mint when they met Dizefalo and watched the evolution of their friendship.

“Mint is kind of really wise but then really naive, I don’t know how to describe it. Mint is very, very trusting,” one friend said.

Two of Mint’s friends tell me that Mint met Dizefalo at Club 9LIVES in Oakland. While Mint saw “something magical” in him, one friend told me they detected something “disgusting” and creepy.

Prior to Dizefalo, Mint had never had a boyfriend. They only had romantic relationships with girls. To Caterina, “My child became a different person overnight. Starting last fall they became a person I didn’t recognize. And I didn’t know what was happening and I didn’t understand it. Mint is a teenager. Teens are full of empathy and love and hormones.”

When I asked about the idea being perpetuated in the media that the 16-year-old was a drug addict, Engeström, who helped raise Mint from age 3, scoffed and said Mint had no involvement with hard drugs before meeting Kio. (I have put various allegations made about Dizefalo to his attorney, and have yet to receive a response.)

The war room is buzzing. Corey Fake, Caterina’s older sister, has been culling through a trove of texts generated by the tip line the FIND MINT team set up. The clock is ticking. Archie pees on a sculpture in protest. He is signaling it is time to go. This is not going to end well. I need to be on a plane Sunday morning.

Caterina paces. “Why aren’t the police doing anything? I have given them Kio’s name and his phone number. Why aren’t they tracking his phone?” I ask her to walk me through her timeline and interactions with police.

According to authorities, on three separate occasions, the FIND MINT team dialed 911 without having any “eyes on,” as in eyes on the victim, which means a confirmed sighting of the target or victim. This is verboten. It is a waste of police resources and interferes with their own attempts to investigate.

Most importantly, if you call police to a known address where the suspect lives you will spook him and the POI (person of interest) will not return there again. Drug addicts, pedophiles, and sociopaths are creatures of habit. Do not try this at home. Police ARE doing their job. “If you want to see Mint alive again, you need to call off the clown show and cooperate fully with police,” I tell Caterina.

I advise that the only way to get Mint back is to allow me to investigate all the tips, coordinate the search, and interface directly with detectives. Relieved, Caterina starts texting madly to tell all the well-intentioned, well-connected contacts to call off all their hired guns. Just then her phone rings. It is someone from one of the volunteer organizations out looking for Mint. They have stopped a van that tipsters had identified as Kio’s means of transportation.

Caterina covers the phone staring at me. “Oh my god, they have Kio. What do I tell them to do?”

40th and Telegraph Road, Oakland, California

11:47 p.m., Thursday, April 25

I am furious. “What should they do? What should I tell them?” asks Caterina. “Well, do they have a tracking device? If they are experienced in surveillance they must have to have a tracking device,” I say.

They did not. Ugh. The problem with running a rogue operation without the police is that only law enforcement has the authority to stop and search a vehicle. These guys have no authority to detain Kio. Now I fear Mint will be driven further underground. Now there’s a high likelihood, the van and that location are blown, which makes the odds of finding Mint more difficult.

“Does anyone have any kind of tracking device they can throw into the van? A phone or ANYTHING?” I ask Caterina.

Caterina had given one of the searchers Mint’s favorite jacket, which had an Apple tracking device sewn into it.

As the searchers talked to Kio, I told one of them to try and place the jacket with the tracking device in the van without causing suspicion. “Give them the jacket and play it cool.”

One of the people who stopped the van later tells me: “At first when we stopped them, we only saw the female driver. We pretended that we were just volunteers out searching for Mint. The person I think was Kio kind of popped his head up when we approached. I showed them the poster, pointed to his picture and Mint’s picture and just asked him if he knew where Mint was.

“He seemed genuine and apologetic, and he said they couldn’t help. I said, ‘Look we’ve been out here looking and Mom’s really worried, can you just help us out? If you see Mint, here’s their jacket, it’s their favorite.’ Nico Snider (a search and rescue operator hired by Caterina) handed Kio the jacket. And while he was talking to Kio, I got a good look in the van. Mint definitely wasn’t there. I slid the door open and shined my light and got a really good look. They weren’t in the van.”

My heart sinks. I don’t say anything, but I fear the teen has been dumped somewhere after overdosing. Still, the jacket’s tracking device does its job—to an extent. We watch as the Apple tag zooms around the East Bay. At 1:47 a.m., it stops moving. It’s been thrown out of the van.

San Francisco, 8 a.m., Friday April 26

Bleary-eyed from being up 48 hours, I pull an all-nighter to read all the tips, confirm their veracity, and then synthesize all relevant information into a report.

Equally important is creating a precise timeline for all investigators (Marin, San Francisco Police, Oakland Police and FBI) to bring them up to speed. I text the lead detective, Lt. Megan Gnoss of Marin County. Caterina contacts all the police agencies to express her intent to fully cooperate. In a conference call with investigators, I share my timeline of Mint sightings in the East Bay, screenshots of the Google maps locations, and promise to keep sending confirmed leads as they come in, including the biggest tip of all—a confirmed sighting of Mint.

San Francisco, 10 a.m., Friday April 26

My phone pings. It’s a video with a date and time stamp. In it is a slight figure walking away from a doorbell camera. That’s Mint!

An alert Oakland citizen, Alison Barakat, has called into the tip line with a confirmed encounter and sighting of Mint in her neighborhood. Barakat was driving her son to school on Wednesday and noticed a small figure sitting on the curb. As they were driving past, Alison remarked to her son that it looked like Mint. “Oh my gosh I think that’s the kid in the missing poster. And my son says ‘Mom, STOP, that’s them.’”

This is the first hard evidence we have that the 16-year-old is alive. The video came to us without an address, yet it revitalized the search. On Google Maps, I pinpoint the house where I think the video was made. It’s the corner of Cavour and Shafter in Rockridge. I send the video and the screenshots to Lt. Gnoss.

I confirm that Kio and the van had been parked on Shafter on Tuesday night and Wednesday. Unbeknownst to the investigation, the homeowners had witnessed the 16-year-old ill on the sidewalk. That same morning, Mara Urizar and Tim Smith had called in a noise complaint to Oakland Police Department because what they said looked like a young girl was vomiting on the sidewalk in a van parked right against their house.

“I was getting my coffee and I saw what I thought was an underage girl lean over,” Mara told me. “She was barely wearing anything at all. Shorts and a tank top and black boots. She definitely looked young. First she vomited blood and then it was cloudy and then it was white.”

Her husband Tim, a retired concrete contractor, took down the license plate and called in a noise complaint. Two Oakland Police Department patrol officers arrived and told the group of three individuals to move on. “Why didn’t the police issue an Amber Alert?” Mara lamented, “I am so upset with myself… I had no idea Mint was missing.” I tell her that, sadly, Amber Alerts are issued by the California Highway Patrol. Mint’s case is not technically a stranger abduction, so it likely did not qualify.

Earlier in the week a woman I will call “D” texted the tip line. She asked not to be identified. “I called because when I heard Kio was with a 16-year-old, I was like, ‘That’s a child,’” she told me. “What’s a 26-year-old man doing with a child?”

D’s friend is 21-year-old “Lucy,” aka Sarah Atkins, whom she identified as the owner of the van. I don’t want to spook her, but I really need her to allow me to speak to her on the phone. After 30 hours of texting, she reaches out. I hold my breath. This is the biggest break in the case.

“I know Kio and he is a bad guy,” says D. Atkins is also Dizefalo’s sometime girlfriend. D says Dizefalo and Atkins are “drug bonded” and fentanyl addicts. “We all OD’d a bunch of times.” Atkins confirms to me what D has said as a true representation of her experience.

I share that the van has been spotted in Rockridge. D tells me that Atkins’ mom lives near there, and that she uses the shower at her mom’s house.

Caterina’s home, 11 p.m., Friday April 26

The last meal I had was in Chicago. That was two nights ago, but stress keeps my hunger at bay. I watch Caterina pace and pace, logging 20,000 steps without ever setting foot outside. This is a woman whose love for her child is ferocious. Asian mothers get a bad rap for being overly controlling and involved. What most do not understand is first generation Asian American mothers come from a tradition of putting one’s child first. Obsessive is an understatement.

My eldest, who is back home from college, is 23 years old, but before I go to bed at night I am already planning what pleasing 16-ingredient breakfast I can serve him. On the other hand, it’s probably been a year since I told him that I love him. Love for Asian mothers is a verb.

Caterina is constantly in motion because Mint is the beating heart of her soul. I’m betting if I asked she can recount the last six meals she fed Mint. I’m terrified that Mint will overdose before we find them. I’m wary that the van stop has spooked Dizefalo, causing him to change locations and vehicles.

San Francisco, Saturday April 27

“D” and I are in full agreement that Mint is vulnerable to Kio’s charms. “At first Lucy was in love with Kio and they talked about getting married and having kids but then it turned. He is despicable,” D says. “I was on the phone with her once when she was trying to get away. She went to the police, but they wouldn’t do anything.” (Atkins confirmed this in a later interview I conducted with her.)

For me, D’s story about Atkins’ exploitation is significant because Dizefalo’s violent past acts help prove child endangerment. I know that sharing this with investigators will show that Mint may not be “voluntarily missing,” but a potential target of exploitation.

What’s critical is that now I finally have Atkins’ name and picture. I type madly and transcribe and send the audio and the transcription to Marin County and SFPD detectives.

Most importantly, we are able to get a clear photograph of Atkins’ face to share. Even though it’s the weekend and Detective Flores is supposed to be on vacation with his wife and 17-year-old twins, he answers my call. “You’re killing me,” Flores tells me. “I’m supposed to have one weekend.”

I know that Flores, who has been with SFPD for 42 years, doesn't believe in weekends. After all, there are 1,400 open cases of missing kids.

San Francisco, 11:57 p.m., Saturday April 27

The updated information about Mint, with the new picture of Lucy and the van driver went out on “SFPD—EVERYONE SWORN,” which is an all-points bulletin that gives officers information on urgent cases. An alert SFPD sergeant reads the bulletin and spots Lucy outside the Parc 55 Hotel at an ATM. He calls it in.

Officers take Dizefalo and Atkins into custody. They fling open all the van doors. It appears empty. The van is surprisingly neat and tidy. There is a large mattress in the back sleeping area. Most officers would likely just shut the van doors but these responders are seasoned in the art of trafficking. Mint Butterfield is found under the mattress in the back of the van. Capt. Alexa O’Brien confirmed that SFPD detained Dizefalo, Atkins, and Butterfield on behalf of Marin County so they could make the arrest and call Mint’s parents.

Tenderloin Police Precinct, San Francisco

1:58 a.m., Sunday April 28

Mint’s parental units—Caterina, Jyri and Stewart—are gathered in the dingy cramped foyer of 301 Eddy St. I walk in and the first thing I think is: His foyer has never smelled so good. Mint’s parents are the shiniest things in the room. No one is hugging or celebratory. While hopeful, I think everyone is tense and wary. An SFPD officer comes to tell the group that they are waiting for the Marin detective to arrive to handle the arrest of the suspects and to officially release Mint to the family. My work is done. When the group informs police they will take Mint straight to the hospital, I push back. This is a very bad idea. “No questions. No interrogation. Just take her home to her cat and her bed.”

Lt. Gnoss comes out to greet everyone. I shake her hand and head to my car. I look at my watch. I’ve got three hours to get to SFO. Ugh. I don’t feel relief yet. The adrenaline is waning. All I feel is tired.

At 2:30 a.m., a week after Mint went missing, their parents take Mint home. Stewart Butterfield sat on the couch talking with Mint, and the exhausted teen eventually fell asleep watching a movie they just started. “It was hard to describe the feelings of relief and gratitude in that moment,” said Stewart. “It was incredible to see Mint safe. I was and am filled with love for Mint and gratitude for everyone, professionals and volunteers, law enforcement, and friends and family, who worked tirelessly to make this outcome possible.”

Undisclosed location, 2 p.m., Sunday, April 28

I’m in the back seat of a chauffeur-driven Cadillac Escalade preparing cotton swabs to surreptitiously collect DNA from the man I suspect of killing dozens of girls as young as 12. Sonoma County and I have been collaborating for four years ever since I worked on the Stanford murders serial killer case.

The lead detective is half-Korean. I tease that Keanu Reeves isn’t good-looking enough to play him in the movie. We are both looking forward to retirement after reeling in Moby Dick. Detectives have promised me that I will get to cuff him when the arrest is made. At the moment, serial killer hunting has never been more glamorous. Stewart Butterfield generously arranged a car and driver because I should not be operating a motor vehicle, having not slept for 78 hours. Sleep won’t be an issue now that I know Mint is home.

The aftermath

After Mint is rescued, one source tells the New York Post that Mint and Dizefalo were “quasi-dating.” (Sgt. Schermerhorn confirmed that he did talk to the Post, but denied saying “quasi-dating.”) When I asked Schermerhorn why he did so many interviews in the early days of the investigation also told me, “I never talked to People magazine.” He added that he did not do any press—except for the press releases issued about the case—until later that week on the Friday when he got “about 40 calls and I didn’t take everyone’s names because it was my day off. I don’t know who I spoke with.”

I reached out with questions for Dizefalo. His attorney, Meredith Maguire, did not return my calls or email inquiries.

Atkins claimed her friends’ accounts of Dizefalo’s abusive behavior towards her was accurate, telling me that she had a job and was his only source of income. When Atkins would try to leave Kio, he “would either threaten to kill himself or he would threaten me.” She alleged being assaulted by him—kicked in the head with his hard boots—and having her van vandalized in response to her trying to leave. An attorney on Atkins’ behalf has approached the DA to communicate her willingness to turn herself in and testify against Dizefalo in this case.

Prosecutors have charged both Dizefalo and Atkins with abducting Mint on April 21. Caterina Fake hopes Marin County District Attorney Lori Frugoli will reconsider their position. In a letter to the DA she wrote: “I feel very strongly that Lucy (Atkins) is a victim as well. She should not be considered a co-conspirator. She helped Mint contact me.”

The judge overseeing the case granted the family’s request for a restraining order preventing Dizefalo from contacting Mint. Dizefalo reportedly told friends that he doesn’t intend to go near Mint as it is “not worth the hassle.”

As of the time of writing, Dizefalo faces charges of child abduction, a felony, and contributing to the delinquency of a minor, a misdemeanor. He pleaded not guilty and is detained on $50,000 bail. He has been ordered not to have any contact with Mint.

According to a criminal complaint, Dizefalo “did willfully and unlawfully, not having a right to custody, maliciously take, entice away, keep, withhold, and conceal a child … with the intent to detain and conceal that child from a lawful custodian, to wit: Caterina Fake and Stewart Butterfield.”

Atkins has been charged with abduction and contributing to the delinquency of a minor. Atkins says she doesn’t know why there is a warrant for her arrest, claims she has been exploited by Dizefalo for years, and is willing to testify against him.

Mint and their family have been reunited, and the parents have declined to have Mint comment, adding that the family itself is focused on recovering. After Mint was found, Fake, Engeström, and Butterfield wrote in a statement, “A heartfelt thanks to all the family, friends, volunteers and strangers who called in tips and made this recovery possible. We especially want to thank the seasoned law enforcement officers who understand the very real threat of predators… There are 1,400 other children missing in San Francisco, and every one of them counts.”

The author, Grace Kahng, produced the award-winning MSNBC documentary series on human trafficking Sex Slaves in America for 10 seasons. Her latest documentary The Stanford Murders is featured on ABC News’ 20/20, and can be streamed on Hulu. Her documentary on human trafficking, Operation Sex Sting, is streaming on Discovery+ and Sling.