text:  Johnson said the country can have intense political discourse, but he said that should never make people a target. Investigators say they still have no idea about what motivated Thomas Matthew Crooks to shoot at Donald Trump. The 20-year-old from Bethel Park outside Pittsburgh was killed by police. The FBI says it's investigating the shooting as a potential act of domestic terrorism, but they have no evidence of any clear ideological motive. They do say, however, that Crooks did act alone.