 Multiple sources tell CBS News that the Secret Service says it was notified of a suspicious person with a rangefinder 20 minutes before the shooting took place in Butler, Pennsylvania. A local tactical sniper inside a neighboring building spotted him from a second floor window and snapped a picture. Crooks pulled out the rangefinder and the sniper alerted his team. Then the shooter climbed on an air conditioning unit to reach the roof of a building near the sniper's position.