 who was perched on a rooftop nearby, maybe 200 to 300 yards away, and was armed with an AR-style rifle that was used to carry out this shooting and was then taken out and killed by a counter sniper with the Secret Service. Let's bring in our senior investigative correspondent, Aaron Katursky, who's been with us all night getting some of this information from law enforcement. Aaron, what else can you tell us about the shooter? But you're also hearing more about the victims.