 New details emerging about the gunman who attempted to assassinate Trump last weekend in Pennsylvania. Law enforcement sources telling ABC News Thomas Crooks was seen walking around near the magnetometers and reported him as suspicious minutes before he climbed a building and began shooting. ABC's Pierre Thomas has more. Sources telling ABC News that police suspect Crooks got on the roof not by using the five-foot ladder he may have recently purchased, but by climbing on top of an air conditioning unit.