 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 down an air conditioning unit to reach the roof of the building near the sniper's position.