Who, exactly, is Trump shooter Thomas Crooks?

A patchwork portrait of the man who tried to kill former President Donald Trump began to emerge early this week after his gunfire killed a spectator at a Butler County, Pa., rally, injured two others, and left the former president bloodied and ducking for cover.

Who, exactly, 20-year-old Thomas Matthew Crooks was, though, remained murky.

He was armed Saturday with an AR-style 5.56-caliber rifle, according to the FBI, and investigators found “rudimentary” explosive devices and bomb-making material inside his car and in the home he shared with his parents in Bethel Park.

He was a registered Republican, records show, and he once donated ActBlue $15 earmarked for the Progressive Turnout Project. His mother was a registered Democrat; his father, a Libertarian who investigators say legally purchased the gun found next to Crooks after he was shot and killed by Secret Service counter-snipers.

A spokeswoman for the Bureau of Alcohol, Tobacco, Firearms and Explosives said investigators were able to quickly trace the gun Crooks used.

“ATF was on the scene within minutes and completed an urgent trace through ATF’s National Tracing Center based on out of business records from a closed gun dealer,” said spokeswoman Kristina Mastropasqua.

She said bureau investigators traced the gun within 30 minutes, helping the FBI and Secret Service to identify Crooks.

Mastropasqua said the bureau was also helping to investigate the explosive devices and apparent bomb-making material.

Federal authorities say they’re investigating Saturday’s shooting not just as an attempted assassination, but a possible act of domestic terrorism. Neighbors and former classmates, though, described Crooks as quiet and relatively unremarkable.

“He seemed like he wouldn’t hurt a fly,” Mark Sigafoos, a Bethel Park High School alum, told CBS News.

He said Crooks was “definitely nerdy, for sure,” but “never gave off that he was creepy or like a school shooter.”

Sigafoos said he sat next to Crooks in an advanced economics class and described him as engaged, approachable and friendly.

“It really makes me wonder what happened in the two years after graduating and maybe what outside influences there were,” he said.

To former classmate Sarah D’Angelo, Crooks was just “Tom.”

“He was a quiet kid. He was nice to anyone he talked to,” she told The Washington Post.

She said he didn’t seem to have had many friends, but also didn’t seem to be lonely. He was smart and took numerous advanced placement classes in high school.

D’Angelo was in an honors history class with Crooks her sophomore year, she told the Post. Their final project for the class was on the assassination of President John F. Kennedy. She said the assignment was to determine what they thought happened, including how many gunmen were involved.

Jason Kohler graduated a year after Crooks. He recalled a kid who sat alone at lunch and was bullied. He said he thought some of the bullying stemmed from his hunting-style attire and his decision to continue wearing a COVID-19 facemask well after the emergent threat of the virus had died down.

Regardless, those who knew Crooks said, the shooting Saturday was wholly unexpected.

“It’s crazy ... you wouldn’t expect that from that kid,” said Dean Sierka, who lives five doors down from the Crooks family and whose daughter went to school with Crooks.

“He was a little bit off, he was like the weird kid, but you wouldn’t expect this.”

Sigafoos said “shocked would be an understatement.”

Crooks’ motive, according to the FBI, remained a mystery. Any public-facing social media has been lost in a sea of hoax accounts. Investigators say there was nothing there that would have foretold the attempted assassination anyway.

On Bethel Park’s Milford Drive — a residential stretch just off busy Route 88 — police blocked the area immediately surrounding the Crooks family’s one-story brick ranch. The community is about 10 miles south of Pittsburgh and 50 miles south of the shooting scene.

Officials in the borough said little other than to confirm that Crooks lived there and graduated from Bethel Park High School in 2022.

Video from the district’s graduation that year shows a tall teenager with what appear to be honors cords over his black graduation gown. He paused and smiled for a photo alongside a woman handing him his diploma. There is the usual scattered applause as his name is called.

A spokesperson for the Community College of Allegheny County confirmed that Crooks graduated in May with an associate’s degree in engineering science.

Throughout the Crooks’ neighborhood on Sunday, curious neighbors eyed the area from the police perimeter and drivers slowed to look as they drove past.

The feeling was one of disbelief.

“Everyone talks about how safe Bethel Park is,” said Lena Skeddle, who moved to the area in2022 from Brazil. “For me, it’s unbelievable.”

Kohler, the Bethel Park alum who graduated a year after Crooks, agreed.

“It’s insane that this is in Bethel Park, this is where I live,” he said. “This is actually unbelievable.”

Staff writers Steve Bohnel and Redmond Bernhold contributed.