By , Pat Milton
/ CBS News
CBS News Live
The gunman who fired shots at former President Donald Trump at a campaign rally in Butler, Pennsylvania, Saturday night has been identified by the FBI as 20-year-old Thomas Matthew Crooks.
Crooks was from Bethel Park, Pennsylvania, about an hour south of Butler.
He was killed by a Secret Service sniper at the rally, officials said.
In a statement, the FBI said:
"The FBI has identified Thomas Matthew Crooks, 20, of Bethel Park, Pennsylvania, as the subject involved in the assassination attempt of former President Donald Trump on July 13, in Butler, Pennsylvania. This remains an active and ongoing investigation, and anyone with information that may assist with the investigation is encouraged to submit photos or videos online at FBI.gov/butler or call 1-800-CALL-FBI."
Federal investigators said the gunman was not carrying identification, so they analyzed his DNA to provide a biometric confirmation of his identity.
One audience member at the rally was killed in the shooting, and two are in critical condition, officials said. Police said the victims were all men; their names have not been released.
Trump said in a social media post that a bullet pierced the upper part of his right ear. He was checked at a local hospital before leaving the area under Secret Service protection and flying to New Jersey late Saturday night.
The gunman opened fire with an AR-style rifle from 200 to 300 feet away from the rally stage, from a position on the roof of a shed outside the security perimeter, multiple law enforcement sources said.
"We do not currently have an identified motive," said Kevin Rojek, FBI Pittsburgh special agent in charge, at a briefing Saturday night.
A man who was at the rally said that soon after Trump started speaking, he saw a man "bear crawling" up the building.
"We're pointing at the guy," said the witness, named Greg, adding, "he had a rifle — you could literally see him with a rifle." He told the BBC that he and others told the police and were pointing him out to U.S. Secret Service agents, and he estimated that the man was on the roof for "three or four minutes" before shots were heard.
Other witnesses told CBS Pittsburgh station KDKA that they also saw the gunman and tried to alert officers before the shooting.
The FBI is leading the investigation into the shooting.
Nicole Sganga is a CBS News reporter covering homeland security and justice.