 Cell phone video shows rally attendees pointing toward the gunman, Thomas Matthew Crooks, trying to alert police two minutes before he opened fire on Mr. Trump. The Butler County, Pennsylvania sheriff says his department wasn't responsible for sweeping the roof where Crooks was positioned. Sources tell CBS News the Secret Service didn't clear it either. President Biden is back on the road. He'll address the NAACP convention in Las Vegas today. Correspondent Nancy Cordes.