After the failed assassination attempt on former Pres. Donald Trump at a campaign event on Saturday, the Secret Service and other law enforcement agencies are facing questions about how a shooter armed with an AR-style rifle was able to get to a rooftop so close to where the presumptive Republican nominee for president was speaking.Carrying an AR-style rifle, Thomas Matthew Crooks, 20, fired multiple shots at the former president standing at the podium less than 150 meters (164 yards) away — one grazing Trump's ear — before a Secret Service agent neutralized him.