US authorities are scrambling to understand how a 20-year-old Pennsylvanian man almost killed former president Donald Trump during yesterday's failed assassination attempt. According to witnesses shooter Thomas Matthew Crooks was seen climbing onto the roof with a rifle several minutes before the first shots rang out. It's the first presidential assassination attempt in the United States in 43 years. It raises serious questions about presidential security.

For more, former Secret Service Agent Cory Allen and former FBI Agent Phil Andrew join.