He was interested in chess and coding, and had recently received an associate degree in engineering science. High school classmates remembered him as an intelligent student who had few friends, but who never exhibited any glaring red flags. The nursing home where he had a job helping with meals said his work gave its staff no reason for “concern”.

And in an era when other people his age put troves of personal information online, Thomas Matthew Crooks, 20, left few clues about who he was, what he believed, or
why he decided to drive to a Trump rally in western Pennsylvania on Saturday and try to assassinate the former President.

On Sunday, federal investigators said a shooter they identified as Crooks had used an AR-15 style rifle purchased by his father to open fire from a rooftop outside the rally where the former President, Donald Trump, was speaking. In a series of new details, FBI officials said they were investigating the incident as a possible case of domestic terrorism, and that the gunman had left behind explosive materials in the vehicle he drove to the event.

But many other details of Crooks’ life and motives of were still unclear. Federal authorities said he had no apparent history of mental health issues or previous threats, and had not been on the radar of federal law enforcement.

Investigators were scouring his online presence and working to gain access to his phone, but so far had not found indications of strongly held political beliefs. In fact, the clues he left behind were confusing: He was a registered
Republican but had also donated to a progressive cause in 2021; his parents were registered as a Democrat and Libertarian.

Crooks was shot and killed by Secret Service agents moments after he began firing, killing a spectator, seriously wounding two others and leaving Trump with an injury to his ear.

Kevin P. Rojek, the FBI official in Pittsburgh who is leading the investigation, said Crooks is believed to have acted alone and that there were no additional public safety concerns.

Attorney general Merrick Garland said that the shooting was “an attack on our democracy” and that federal authorities would use every available resource to investigate the shooting.

Crooks grew up in the relatively affluent suburb of Bethel Park in the South Hills region of Pittsburgh, about an hour’s drive from the site of the rally.

His parents are both licenced counsellors, according to Pennsylvania records.

His father worked at a local behavioural health provider, according to his LinkedIn profile.

The neighbourhood where the family lives is “pretty firmly middle class, maybe upper-middle class”, Dan Grzybek, who represents the area on the county council, said in an interview on Sunday.

Grzybek briefly met the gunman’s parents last year when he was canvassing for his run. He did not recall the exact conversation, but he remembered they seemed pleasant.

Just two months ago, Crooks graduated from the Community College of Allegheny County with an associate degree in engineering science, a school official said.

Crooks had been working as a dietary aide at Bethel Park Skilled Nursing and Rehabilitation Center. Marcie Grimm, the facility’s administrator, said the organisation was shocked to learn of his involvement in the shooting.

New York Times News Service