A suspected gunman who opened fire during a Trump rally Saturday in Butler, Pennsylvania, was fatally shot by a Secret Service sniper, authorities said. 

One rally attendee was killed and two more were critically wounded, the Secret Service said in a statement Saturday night.  

The suspect was shot and killed by a member of a Secret Service counter-assault team, two law enforcement sources told CBS News. 

Multiple law enforcement sources said the gunman was outside of the cordoned-off rally area, about 400 feet from the stage, and was on top of a shed, the two sources said. The shooter was armed with a semi-automatic AR-15 rifle, the sources said. ATF is tracing the weapon.

Several shots rang out while Trump was speaking on stage at about 6:15 p.m. local time. Video showed the former president immediately touch his ear and then crouch to the ground, with his Secret Service agents rushing the stage. Some blood could be seen on his face as he stood up and held up his fist to the crowd. He was rushed out to his motorcade and the Secret Service later confirmed that he was safe.   

In a post to his Truth Social platform, Trump said he was "shot with a bullet that pierced the upper part of my right ear."

"I knew immediately that something was wrong in that I heard a whizzing sound, shots, and immediately felt the bullet ripping through the skin," he continued.

Authorities are investigating the shooting as an attempted assassination. The FBI said in a statement that it is leading the investigation, with assistance from the Secret Service and state and local agencies. 

In a statement early Sunday morning, the FBI identified the shooter as 20-year-old Thomas Matthew Crooks of Bethel Park, Pennsylvania, which is located just outside Pittsburgh.   

In a news conference late Saturday night, Kevin Rojek, special agent in charge of the FBI Pittsburgh office, refused to speculate on a possible motive. He disclosed that "there was identification of suspicious packages around where the shooter was, and so we deployed, in an abundance of caution, bomb assets, to make sure those were cleared for investigators."

The FBI is leading the investigation, with assistance from the Secret Service and state and local agencies. 

Rally attendee Ben Macer told CBS Pittsburgh that he saw the suspect "move from roof to roof" and told an officer that the gunman "was on the roof."

"When I turned around to go back to where I was, it was when the gunshots started, and then it was just chaos, and we all came running away, and that was that," Macer said. 

Rep. Mike Kelley of Pennsylvania, who was standing backstage watching Trump speak, told CBS News, "I believe a lady who was next to me was hit, other people were hit."  

Dr. Jim Sweetland, an emergency room physician who was at the rally and witnessed the shooting, told CBS News by phone that he administered first aid to a man who had sustained a gunshot wound to the head.

"He was shot in the head, his body was twisted around and wedged between two benches that were in the stands," Sweetland said. "He was not breathing, he did not have a pulse. He appeared gravely ill."

With the help of three people, Sweetland said he was able to get the victim onto a bench and then began administering CPR and chest compressions.

"There was a lot of blood that was spilt on the stands where he lay, as well as brain matter," Sweetland said.

Two Pennsylvania State Police troopers then approached, gathered up the victim and took him, presumably to an ambulance, Sweetland said. 

Republican Senate candidate David McCormick, who was in the front row of the rally, also saw one person shot.

"It was really hard to tell, there was a lot of blood, so it wasn't clear where the bullet had struck him, and how severe the wound was," McCormick told CBS News. "He looked to be unconscious, but even that's not entirely clear to me."

The shooting comes just two days before the start of the Republican National Convention in Milwaukee. 

Trump's motorcade departed Butler Memorial Hospital a little before 9:30 p.m. local time, two sources confirmed to CBS News. Video posted by a Trump aide to social media early Sunday morning showed him deboarding after his plane landed at Newark Liberty International Airport in New Jersey. Prior to the shooting incident, he had been scheduled to travel to his estate in Bedminster, New Jersey, before departing for Milwaukee for the convention.

In:
• Donald Trump

Faris Tanyos

Faris Tanyos is a news editor for CBSNews.com, where he writes and edits stories and tracks breaking news. He previously worked as a digital news producer at several local news stations up and down the West Coast.