 Two days after a gunman tried to assassinate President Donald Trump, authorities are still trying to figure out what could have motivated the 20-year-old would-be assassin. John Stolmas is following the latest. Homeland Security Secretary Alejandro Mayorkas says they will be conducting an independent investigation into the assassination attempt on the Republican nominee for president. The Secret Service has taken criticism from some after the gunman, Thomas Matthew Crooks, was able to ascend to an adjacent rooftop with a clear line of sight of the president.