 rally in Pennsylvania last weekend, and there are new details surfacing about the shooting and the suspect, 20-year-old Thomas Crooks, ABC's Jay O'Brien's in Grand Rapids. Authorities now investigating whether Crooks used a drone to survey the rally location prior to the shooting. A comprehensive timeline reviewed by ABC News found law enforcement first spotted the shooter at least an hour before he opened fire, and a sniper had eyes on him up until six minutes before the shots rang out.