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Editor’s note: This story has been updated to correct the distance between Bethel Park and Butler, Pennsylvania.

(NewsNation) — The FBI said Sunday the attempted assassin at President Donald Trump’s rally was a 20-year-old man named Thomas Matthew Crooks. Secret Service shot and killed Crooks seconds after Trump was shot.

The attack is the most serious attempt to assassinate a president or presidential candidate since Ronald Reagan was shot in 1981.

Law enforcement officials told the Associated Press that bomb-making materials were found inside a vehicle linked to the suspect in the Trump rally shooting. There were also bomb-making materials found at his home. The two officials were not authorized to speak publicly and spoke to the AP on condition of anonymity.

The former president, according to Trump campaign officials, is “fine.”

Who is Thomas Matthew Crooks?

Crooks is from Bethel Park, Pennsylvania, about 60 miles from where the rally was held in Butler, Pennsylvania. NewsNation has learned neighbors of the suspected shooter were evacuated from their homes Sunday in Bethel Park.

Per state records, he’s a registered Republican, but the Associated Press reports he donated $15 to a progressive PAC the day President Joe Biden was sworn in.

Crooks was a dietary aide at the Bethel Park Skilled Nursing and Rehabilitation Center, the organization said in a statement Sunday, The Hill reported.

The center also said workers were “shocked and saddened” to hear he was involved.

“This morning, Bethel Park Skilled Nursing and Rehabilitation Center became aware that Thomas Matthew Crooks, a dietary aide at the Center, was the alleged shooter in the assassination attempt on Former President Trump,” Marcie Grimm, the administrator for the center, said in a statement.

“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,” she continued. “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 Secret Service said one rally attendee was killed and two were critically injured.

The deceased victim was identified Sunday as former Butler County Fire Chief Corey Comperatore. The 50-year-old father was protecting his family from the bullets before he was struck, according to his sister, Dawn, Pennsylvania Gov. Josh Shapiro said at a news conference Sunday.

The agency said Crooks fired from “an elevated position outside the rally venue.” All three victims are adult males, police said.

The FBI said they have no reason to believe there is an ongoing threat.

Bethel Park School District confirms Crooks’ identity

In a Sunday news release, Bethel Park School District expressed condolences for those injured by its Class of 2022 alumnus.

“The school district wishes to express its sincere wishes for a speedy and complete recovery for Mr. Trump and those in attendance at the Saturday event who may have been physically harmed or emotionally impacted by these tragic events. We offer special condolences to the family of Mr. Corey Comperatore, who was killed. Our thoughts and prayers are with you at this difficult time.”

The district plans to “cooperate fully” with law enforcement as investigation continues, meaning “we are limited in what we can publicly disclose.”

Jason Kuhler, a high school classmate of Crooks, told NewsNation affiliates that he sat alone at lunch and was bullied.

“I didn’t have any classes with him. My only interactions with him were just seeing him in school,” Kuhler said.

Kuhler said he found out the shooter was Crooks by word of mouth and internet updates. “And we were like, ‘Wow, this is insane.'”

“I mean, this is where I live. I never thought this would be going on in a town I’ve grown up in my whole life,” he added. The classmate did not have any information about a potential motive.

Crooks bullied, a loner: Former classmate

A classmate told NewsNation that Crooks attempted to join the Bethel Park High School Rifle Club but was not invited back because he was “a bad shot.”

The classmate also said Crooks was a loner who was allegedly bullied in school.

According to The Hill, Crooks was part of a BlackRock ad filmed at Bethel Park High in 2022. The advertisement centered around management of public school teachers’ retirement plans.

Crooks graduated from the high school in 2022.

Crooks had legal gun, no indication of mental issues

Senior FBI officials confirmed to NewsNation’s Evan Lambert that Crooks had “no indication of mental health issues,” and that no threats toward the president or event have been found.

Officials also said a legally obtained AR-style rifle utilizing 5.56×45 mm ammo was located “at scene adjacent to shooter.” It was purchased by Crooks’ father, but how the 20-year-old accessed it is unknown at this time. The shooter’s family is cooperating with law enforcement.

Investigation is ongoing into Crooks’ social media consumption and cellphone history. The scene is still being processed, and DNA, weapon and fingerprint testing continues.

More than 2,000 tips regarding Crooks have been received. Anyone with more information is asked to call 1-800-CALL-FBI.

Did Thomas Matthew Crooks act alone?

FBI officials said Sunday there is nothing to indicate another actor was involved in the shooting.

When asked whether the deceased suspect acted alone Saturday, Pennsylvania State Police Lt. Col. George Bivens said: “It will be some time until we can conclusively say or answer that question.”

“We are not taking for granted that this was a lone wolf attack,” Bivens said.

Two officials who spoke to the Associated Press on the condition of anonymity to discuss the investigation said Crooks was not an attendee.

Where was Trump rally shooter?

A video posted to social media and geolocated by AP shows the body of a person wearing gray camouflage lying motionless on the roof of a building at AGR International Inc., a manufacturing plant just north of the Butler Farm Show grounds where Trump’s rally was held.

The roof where Crooks lay was less than 150 meters (164 yards) from where Trump was speaking, a distance from which a decent marksman could reasonably hit a human-sized target. For reference, 150 meters is the distance at which U.S. Army recruits must hit a scaled human-sized silhouette to qualify with the M-16 rifle.

NewsNation sources say the building was assigned to local authorities to cover; a standard procedure for locales outside the perimeter at events. The Secret Service is still investigating how Crooks got on the roof.

Eyewitness accounts of the shooter

Witnesses told media outlets they saw Crooks on a roof outside the rally.

Easton Smith, who was outside the security perimeter at the rally, said he saw a man climbing up the roof of a nearby building.

“Didn’t know what he was doing, trying to alert cops and police there was a guy crawling on the roof,” Smith said. “Then we saw a rifle slinged over his shoulder. After that, a couple shots fired off.”

A witness named Greg Smith told BBC News that Crooks had crawled on top of the building located just outside the event. He said he pointed the gunman out to police.

“I’m thinking to myself, ‘Why is Trump still speaking, why have they not pulled him off the stage’ … the next thing you know, five shots ring out.”

Smith was listening from outside the rally and said he saw the gunman around five minutes into Trump’s speech.

“We noticed the guy bear-crawling up the roof of the building beside us, 50 feet away,” he said. “He had a rifle, we could clearly see a rifle.

“We’re pointing at him, the police are down there running around on the ground, we’re, like, ‘Hey man, there’s a guy on the roof with a rifle’… and the police did not know what was going on.”

Smith said he tried to alert the authorities for three to four minutes, but thought they probably could not see the gunman because of the slope of the roof.

One local police officer told AP he climbed to the roof and encountered Crooks, who pointed his rifle at the officer. The officer then retreated down the ladder, and Crooks quickly took a shot toward Trump.

That’s when Secret Service snipers shot him, said the officials, who spoke to AP on condition of anonymity to discuss an ongoing investigation.

“Why is there not Secret Service on all of these roofs here?” he asked. “This is not a big place. (It’s a) security failure, 100% security failure.”

He said he later saw the agents shoot the gunman: “They crawled up on the roof, they had their guns pointed at him, made sure he was dead. He was dead, and that was it — it was over.”

Two firefighters from nearby Steubenville, Ohio, who were at the rally told the AP that they helped people who appeared injured and heard bullets hitting broadcast speakers.

“The bullets rattled around the grandstand, one hit the speaker tower and then chaos broke. We hit the ground and then the police converged into the grandstands,” Chris Takach said.

“After we heard the shots got fired, then the hydraulic line was spraying all around, you could see the hydraulic fluid coming out of it. And then the speaker tower started to fall down,” Dave Sullivan said. “Then we heard another shot that you could hear, you knew something was, it was bullets. It wasn’t firecrackers.”

Law enforcement response

Trump was examined at a Butler, Pennsylvania, medical facility after shots were fired. Trump ducked behind a podium and was rushed off by the Secret Service. In a post on Truth Social, Trump said he felt a bullet hit his ear during the shooting.

He was later released from the medical facility.

This incident is currently under investigation and “the Secret Service has notified the FBI,” said Anthony Guglielmi, Secret Service chief of communications.

The FBI said it has assumed the role of the lead federal law enforcement agency in the investigation.

Police soon told the people remaining to leave the venue, and Secret Service agents told reporters to get “out now. This is a live crime scene.”

A copy of an email from a source with the Republican National Committee shows Trump campaign staffers being asked to stay away from the D.C. and Palm Beach, Florida, offices.

“In response to this violence, we encourage those of you who remain in DC and West Palm Beach to stay away from the office tomorrow, as we assess both locations,” the email reads. “We are enhancing the armed security presence with 24/7 officers on-site.”

In a statement released Monday afternoon, the FBI announced it had gained access to Crooks’ phone and have searched his residence and vehicle.

The FBI have also conducted nearly 100 interviews with witnesses and law enforcement personnel. Their investigation is ongoing.

The Associated Press contributed to this report.