Investigators believe gun used in Trump's apparent assassination attempt bought by suspect's father

'He kept to himself': Former classmate of shooter The FBI has identified the shooter as 20-year-old Thomas Matthew Crooks who former classmates describe as 'lonely and quiet'.

A shooting at Donald Trump‘s rally in Butler, Penn., is being investigated as an attempted assassination of the former U.S. president and presumptive Republican nominee, law enforcement officials say.

Two law enforcement officials tell The Associated Press investigators believe the weapon was bought the father of Thomas Matthew Crooks, who's been identified as the shooter, at least six months ago.

The officials said federal agents were still working to understand when and how Crooks obtained the gun and gather additional information about him as they worked to try to identify a possible motive.

The investigation is focused on Crooks.

The officials were not authorized to publicly discuss details of the investigation and spoke to the AP on condition of anonymity.