Law enforcement officials revealed that the gunman who attempted to kill Donald Trump managed to fly a drone over the western Pennsylvania fairgrounds just before Trump’s scheduled speech, highlighting significant security lapses.

Thomas Matthew Crooks used the drone on July 13 to survey the Butler Farm Show grounds. He fired at least six rounds from the roof of the American Glass Research building, 400 feet away, killing one spectator and critically injuring two others, while Trump sustained a graze wound to the ear.

A Secret Service sniper team killed Crooks, whose motive is still unknown. Multiple investigations are ongoing into the security breach.