The gunman who tried to assassinate former President Donald Trump accessed his rooftop vantage point by first climbing onto an air conditioning unit, sources told NBC News. Matthew Thomas Crooks, the 20-year-old shooter, climbed onto the roof of a building at the Butler Farm Show Grounds in July before taking eight shots at the Republican nominee. Crooks managed to graze Trump’s ear while injuring three attendees and killing one man. However, it remains unclear how Crooks was able to get on the rooftop without alerting security. According to the sources, Crooks was caught on security footage from a nearby ice cream shop climbing onto the building’s air conditioning unit. It is unclear if the security footage will ever be released to the public. Secret Service Director Kimberly Cheatle resigned after testifying before congress about the security failings, and multiple secret service agents were reportedly put on leave on Friday.