 ABC News Chief Justice Correspondent Pierre Thomas. Sources tell ABC News that a short time before the former president took to the podium, local authorities were alerted to suspicious activity on the outside of the perimeter and were in the process of looking for a suspect. Ryan Knight attended the rally. I look over at the AGR building and there's a guy going prone. And saw the shooter open fire. Guy starts taking shots at the president. He's raising serious questions. Why the Secret Service was not on top of that building.