US authorities said that the man who attempted to kill former President Donald Trump acted alone and there is no sign of foreign involvement.

But FBI officials stressed at a news briefing on Wednesday that a motive for the assassination attempt remains unknown, and they said that Thomas Crooks – the 20-year-old assailant – had a “mixture of ideologies”.

The law enforcement agency described Crooks’s search history, and it released photos of the gun he used and the improvised explosive devices found in his car.

Crooks attempted to shoot the former president at a rally in Butler, Pennsylvania, on 13 July. He grazed Trump’s ear, killed one man and seriously injured two others.

Kevin Rojek, head of the FBI’s Pittsburgh office, said that Crooks began searching online for Trump campaign events starting in September 2023.

He searched for events for both Trump and President Joe Biden, who was still the Democratic nominee at the time of the shooting. He also looked for the location of both the Republican and Democratic national conventions.

“When… the Trump rally was announced early in July, he became hyper-focused on that specific event and looked at it as a target of opportunity,” Mr Rojek said.

Crooks registered for the Trump rally one week in advance, Mr Rojek said.

On the same day, the 20-year-old searched how far assassin Lee Harvey Oswald was from John F Kennedy when the Marine veteran fatally shot the US president in 1963.

Crooks also looked up “Where will Trump speak from at Butler Farm Show?” – the site of the rally. His search history showed that he had attempted to find bomb making instructions and ingredients as well, authorities said.

“We believe the subject engaged in detailed attack planning,” Mr Rojek said.

FBI officials said Crooks’s online activities showed a “mixture of ideologies” and that they are continuing to look into his online presence.

“We see no definitive ideology associated with our subject, either left leaning or right leaning,” Mr Rojek said.

Crooks was a registered Republican. In 2021, he donated $15 to liberal campaign group ActBlue.

Officials said that some anti-Semitic comments online “were associated with accounts associated with [Crooks]” and that they were working to determine whether he wrote them.

The FBI has previously said that Crooks had at least two social media accounts which showed contradictory ideological views. The content of the accounts has not been made public.

At the Butler rally, Crooks was on the roof of a nearby building for about six minutes. He fired eight shots at Trump, who was speaking on a stage, before a Secret Service sniper killed him.

During Wednesday’s news conference, FBI officials also responded to criticism by conservatives, including Republican Congressman Clay Higgins of Louisiana, that the agency had cleaned up the crime scene and returned Crooks’s body to his family too quickly.

Mr Rojek said that standard procedures were followed in the clean up of the site, that Crooks’s body was returned after an autopsy was completed and that it is not standard procedure to retain human remains indefinitely.

The autopsy indicated that Crooks had no trace of illegal drugs or alcohol in his system. The FBI said that the Crooks family has co-operated with their investigation.

A Congressional task force including both Republicans and Democrats is in the process of investigating the security failures that led to the shooting.

Kimberly Cheatle, the director of the Secret Service at the time of the shooting, stepped down from her position last month after facing intense pressure from lawmakers.

She has since been replaced by Ronald Rowe as acting director.

At least five Secret Service agents have been placed on administrative leave following the security lapse.

Last week, Trump held an outdoor rally in North Carolina – his first since the assassination attempt. He appeared behind a podium surrounded by bulletproof glass.