 Federal law enforcement sources tell us it was local law enforcement who had responsibility for securing the rooftop. It was rally goers who first spotted the gunmen crawling on top of the building. Sources tell us one officer climbed to the top of the roof, saw crooks armed with a rifle and retreated. Soon after that, crooks began to fire, according to the source. And we know moments later, a Secret Service counter sniper shot and killed the gunman.