 Update on the assassination attempt a week ago at a Pennsylvania rally with gunman Thomas Crooks from ABC's Jay O'Brien. 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. One sniper even meeting with law enforcement on the ground to tell them the shooter's location.