A 20-year-old Pennsylvania man, Thomas Matthew Crooks, who tried to assassinate former United States president Donald Trump at a campaign rally this weekend.
killed Crooks after he fired multiple shots at the rally in Butler, Pennsylvania, from a nearby rooftop.
As authorities seek to understand his motivations, here's what we know of the alleged gunman.
Thomas Crooks described as 'quiet', 'lonely'
The early details that have emerged about Crooks show a young man working an entry-level job near his hometown in Pennsylvania, where he graduated from high school in 2022 with a reputation as a bright but quiet classmate.
The Federal Bureau of Investigation (FBI) said that his social media profile does not contain threatening language, nor have they found any history of mental health issues. The agency says he acted alone and has not identified a motive.
Crooks' former schoolmates described him as a "quiet" student who often came across as "lonely," ABC News reported.
Thomas Matthew Crooks graduated from high school in Pennsylvania in 2022. Source: AFP / Handout
Trump, 78, was hit in the ear at the rally. A bystander was killed and two spectators were critically injured.
Jason Kohler, who said he attended school with Crooks, said that the alleged shooter had often been bullied.
Donald Trump was bundled into a car by Secret Service agents after the shooting at his campaign rally. Source: AAP / Gene J. Puskar/AP
He said Crooks had been teased for how he dressed, noting that he would sometimes wear hunting outfits.
Dan Grzybek, a county council representative in the area where Crooks grew up, said the neighbourhood was "pretty firmly middle class, maybe upper-middle class", according to The New York Times.
The Times added that Crooks had been working at a nursing home, and the organisation was shocked to hear of his involvement in the shooting.
"We are shocked and saddened to learn of his involvement as Thomas Matthew Crooks performed his job without concern and his background check was clean," Marcie Grimm, the administrator of the Bethel Park Skilled Nursing and Rehabilitation Centre, said.
Crooks had no military ties
Following the incident, investigators found a "suspicious device" in Crooks' car, which was inspected by bomb technicians and is being analysed.
They noted that suspected explosive devices have been collected as evidence.
Authorities are now in the process of searching Crooks' phone.
Kevin Rojek, special agent in charge of the FBI's Pittsburgh field office, told reporters that the gun used in the shooting was an AR-style semi-automatic rifle purchased legally.
Investigators believe the weapon was purchased by Crooks' father.
Rojek added that there were no indications so far of any mental health issues.
Crooks also did not have military affiliations, according to Pentagon spokesperson major general Pat Ryder.
The FBI told reporters that they are investigating the incident as an assassination attempt and also a potential domestic terrorism act.
Crooks acted alone
The shooter was believed to be working alone, according to the FBI, and officials said they have not identified an ideology associated with him.
His political leanings were not instantly clear.
News reports indicated he was a registered Republican, but also noted that he previously gave money to a Democratic-aligned progressive political action committee.
Social media platform Discord said it had identified an account that appeared linked to the suspect, but it was "rarely utilised".
A spokesperson added that "we have found no evidence that it was used to plan this incident, promote violence, or discuss his political views".
The suspect's father Matthew Crooks told CNN that he was trying to establish "what the hell is going on" before speaking about his son.
Trump rally victim was a firefighter and a father
The spectator who died in the shooting has been identified as Corey Comperatore, a 50-year-old firefighter and father of two.
"We lost a fellow Pennsylvanian last night, Corey Comperatore," the state's governor, Josh Shapiro, told reporters. "I just spoke to his wife and his two daughters."
He said the victim was a churchgoing firefighter and an enthusiastic Trump supporter who "loved his community and most especially ... his family."
The other victims have not been identified yet, though NPR news affiliate WESA quoted hospital officials in Pittsburgh as saying both were local men and both remained in critical condition.
