What to know An investigation is ongoing after a gunman opened fire on former President Donald Trump at a rally Saturday in Butler, Pennsylvania, injuring him.Corey Comperatore, 50, a former chief of the Buffalo Township Volunteer Fire Company, was shot and killed, while two others — David Dutch, 57, and James Copenhaver, 74 — were injured.The shooter has been identified as Thomas Matthew Crooks, 20, of Bethel Park. He was a member of a local gun club and worked as a dietary aide at a nursing facility.More than a dozen guns were found in a search of the Crooks family home, four senior officials told NBC News. Authorities have not been able to determine a motive for the attempted assassination.