Who was Thomas Matthew Crooks, the Trump rally shooter?

• The FBI identified Thomas Matthew Crooks as the man who shot at Donald Trump.
• Crooks was a 20-year-old from Bethel Park, Pa., and was shot dead by a Secret Service sniper.
• Crooks was a registered Republican. His motivation for shooting at Trump remains unclear.

The FBI has identified the man who shot at former President Donald Trump as Thomas Matthew Crooks, a 20-year-old from Bethel Park, Pennsylvania.

Crooks was shot dead by Secret Service agents after he fired from "an elevated position" at Trump during a rally in Pennsylvania on Saturday.

Trump said he was hit in the upper part of his ear with a bullet, but his campaign said the president was "fine." A bystander at the rally was killed in the attempted assassination.

Here's the latest on what we know about Crooks:

July 15, 8 a.m.: Crooks bought ammunition just before the shooting

Crooks bought 50 rounds of ammunition from a local gun store hours before the attempted assassination, CNN reported .

July 14, 8:27 p.m.: Crooks belonged to a local gun club

CBS News first reported that Crooks was a member of the Clairton Sportsmen's Club, a club with multiple pistol and rifle ranges in Clairton, Pennsylvania.

"Obviously, the Club fully admonishes the senseless act of violence that occurred yesterday," Bill Sellitto, the president of the club told CBS. "The Club also offers its sincerest condolences to the Comperatore family and extends prayers to all of those injured including the former President."

CBS also reported, citing a law enforcement source, that Crooks had at the time of the shooting been wearing a t-shirt that read "DemolitionRanch," an apparent reference to a gun-related YouTube channel with over 11 million subscribers.

July 14, 3:47 p.m.: FBI confirms details about gunman's weapons

In a call with reporters, FBI Pittsburgh Office Director Kevin Rojek said Crooks used an "AR-style 5.56 rifle" that was legally purchased to shoot Trump and the bystander.

Rojek also said the FBI hasn't finished a comprehensive assessment of the "rudimentary" explosive devices that were found among Crooks' possessions.

It remains unclear whether Crooks encountered local law enforcement before opening fire on Trump.

"We're still trying to flesh out those details," Rojek said.

July 14, 3:37 p.m.: Crooks likely acted alone, had no mental health issues, FBI says

Rojek said the FBI's initial investigation indicates that Crooks acted alone, and authorities have not yet "identified an ideology" related to the shooting.

"At this time, we have no indication of mental health issues," Rojek said. "Our primary focus is on the phone. We are working to get access to the phone."

Robert Wells, the assistant director of the Counterterrorism Division, said the FBI's top priority is identifying a motive and assessing whether there were co-conspirators, though there are currently no indicators of other people involved.

"We are investigating this as an assassination attempt but also looking at it as a potential domestic terrorism act. So our counterterrorism division and our criminal divisions are working, working jointly together to determine the motive," Wells said.

Officials are combing Crooks's social media accounts and monitoring accounts from people pretending to be the gunman, Rojek said.

July 14, 3:07 p.m.: Crooks worked at a nursing center

Crooks was a dietary aide at the Bethel Park Skilled Nursing and Rehabilitation Center, the center said in a statement obtained by The Hill on Sunday.

"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," a spokesperson for the center said in the statement. "We are fully cooperating with law enforcement officials at this time. Due to the ongoing investigation, we cannot comment further on any specifics. Our thoughts and prayers go out to Former President Trump and the victims impacted by this terrible tragedy. We condemn all acts of violence."

The center did not immediately respond to Business Insider's request for comment.

July 14, 2:12 p.m.: Biden cautions not to assume motive

During a brief press conference from the White House, President Joe Biden said investigators had not yet determined Crooks' motive.

"I urge everyone, please: don't make assumptions about his motives or his affiliations," Biden said. "Let the FBI do their job."

Biden said he has ordered investigations into the shooting be "thorough and swift."

The president said he would speak more during a primetime address on Sunday night.

July 14, 12 p.m.: Explosives found: reports

The Wall Street Journal cited anonymous people briefed on the case that authorities later found explosive devices in Crooks' car, which he had driven to the rally and parked up nearby.

Police received reports of suspicious packages in the area surrounding the shooter, and bomb technicians were dispatched to the scene, per The Journal.

Law enforcement also found materials to make a bomb at Crooks' home, according to The Associated Press .

The FBI told Business Insider that the investigation into the shooting is still ongoing. Investigators haven't determined Crooks' motive as of Sunday morning.

July 14, 10 a.m.: AR-style rifle was reportedly used in the shooting

Law enforcement found an AR-15-type semiautomatic rifle near Crooks' body, according to The New York Times.

Law enforcement officials told The Associated Press that investigators believed the weapon to have been bought by Crooks' father.

Who was Thomas Matthew Crooks?

Voting records showed Crooks was registered as a Republican.

Crooks doesn't appear to have a criminal record before the shooting, according to online Pennsylvania court records.

Federal Election Commission records revealed that someone matching Crooks' name and address made a $15 donation in January 2021 to the Progressive Turnout Project via ActBlue, a platform that raises funds for political candidates.

The upcoming election in November would have been the first time Crooks would have been old enough to vote in a presidential race.

It is not yet clear what his motivation was for shooting at the former president.

The Bethel Park School District in Pennsylvania confirmed in a statement seen by local media that Crooks had graduated from Bethel Park High in 2022.

"Our school district will cooperate fully with the active law enforcement investigation surrounding this case," the statement read.

According to local media outlet Triblive, Crooks had received a $500 "star award" from the National Math and Science Initiative.

Crooks made a brief appearance in a 30-second BlackRock ad from 2022.

The money manager said on Sunday that it had removed the ad, which was focused on an AP Economics teacher from Bethel Park High School. Crooks graduated high school in 2022.

"In 2022, we ran an ad featuring a teacher from Bethel Park High School, in which several unpaid students briefly appeared in the background, including Thomas Matthew Crooks," BlackRock said in a statement to Reuters . "The assassination attempt on former President Trump is abhorrent."

An ex-elementary and high school classmate of Crooks', Jameson Myers, told ABC News that Crooks didn't make the cut for the high school rifle team because of his poor marksmanship .

"He didn't just not make the team, he was asked not to come back because how bad of a shot he was, it was considered like, dangerous," Myers said.

When approached for comment, Crooks' school district told ABC News that he had "never appeared on a roster" and that there was "no record" of him trying out.

According to reports from USA Today, dozens of law enforcement vehicles were stationed outside the address listed on Crooks' voter registration record as of Sunday morning. Roads leading to the house were shut down.

Agents from the Bureau of Alcohol, Tobacco, Firearms and Explosives were on the scene, according to the outlet. A bomb squad was also in attendance.

Crooks' residence is about an hour's drive south of Butler.

Crooks' father, Matthew Crooks, 53, told CNN that he was trying to figure out "what the hell is going on" and would wait until he spoke to law enforcement before speaking about his son.