BUTLER, Pennsylvania — We’re learning more about the man suspected in the shooting at a campaign rally for former President Donald Trump in Butler, Pennsylvania on Saturday that left one spectator dead, two others critically injured and sparked chaos at the event.

The FBI has identified 20-year-old Thomas Matthew Crooks of Bethel, Pennsylvania as the subject involved in the assassination attempt. Officials say the suspect was shot and killed, taken down by a Secret Service countersniper.

According to a law enforcement source, the early indication is that the shooter was a lone wolf, but the situation is fluid and the agency is still trying to assess a motive for the shooting.

Officials at a press conference late Saturday said they needed to do DNA testing, because the suspected shooter did not have ID.

“It’s a matter of doing biometric confirmations, so there was no identification on the individual for example so we’re looking at photographs right now and we’re trying to run his DNA and get biometric confirmation,”

FBI Pittsburgh Special Agent in Charge Kevin Rojek said.

In a statement on Truth Social posted hours after the shooting, Trump said he “was shot with a bullet that pierced the upper part of my right ear.”

LIVE UPDATES | Trump rushed off stage at rally after possible assassination attempt

“I knew immediately that something was wrong in that I heard a whizzing sound, shots, and immediately felt the bullet ripping through the skin. Much bleeding took place, so I realized then what was happening,” he wrote in the post, which expressed condolences to the family of the rallygoer who was killed.

A Trump spokesperson says the president was checked out and is fine.

Officials briefed on the investigation told ABC News that the shooting — a chilling development on the eve of the Republican National Convention — was being investigated as an assassination attempt and that live rounds were apparently fired from outside the security perimeter. It is being investigated by the FBI overseen by the Justice Department’s National Security Division as well as the U.S. attorney’s office in Pittsburgh and comes amid a heightened threat environment.

PHOTOS: Shots fired at Trump rally in Pennsylvania

The Secret Service, in a statement, said that a shooter “fired multiple shots toward the stage from an elevated position outside of the rally venue” after which agents “neutralized the shooter, who is now deceased.”

Take a look at the latest updates on the deadly shooting here.