Would-be Donald Trump assassin Thomas Matthew Crooks looked up pornography not long before he shot at the former president.
The search was the last one Crooks, 20, made on his phone before wounding Trump as he spoke at a rally in Butler, Pennsylvania, last Saturday.
FBI investigators discovered the search history after finally cracking his encrypted Samsung Android phone days after the assassination attempt.
Other queries included Princess Kate as well as her fellow British royals, both Trump and President Joe Biden, and school shooter Ethan Crumbley.
Donald Trump's would-be assassin Thomas Matthew Crooks used his last internet search to look up pornography
The senior law enforcement source who told the Daily Beast about the porn search said it was 'not unusual' among high-profile killers.
Sandy Hook elementary school mass shooter Adam Lanza had child abuse images on his phone and Al Qaeda terrorists also watched extreme porn.
Agents couldn't initially break into Crooks' phone and sent it to the Operational Technology Division at FBI headquarters in Quantico, Virginia.
The only other recent activity on his phone was texts from his parents asking where he was after he didn't come home from the gun range when they expected.
Crooks was shot dead by Secret Service sharpshooters after his shots grazed Trump's ear, killed rally attendee Corey Comperatore, and wounded another.
Investigators have moved on to his laptop and external hard drives found during a search of his parents' home, where he lived.
Crooks had images of the Princess of Wales on his phone, sources told DailyMail.com, and also looked up FBI Director Christopher Wray and US Attorney General Merrick Garland.
It is not yet clear why Crooks was looking up Kate - the only non-American in the group of people found in his internet search history.
Gunman Thomas Crooks (pictured) also researched Princess Kate during his assassination planning, the FBI revealed
Donald Trump (pictured) narrowly avoided being killed by a gunman on Saturday during a rally. He was struck on the ear when he turned his at the last second
The Princess of Wales has only conducted limited public appearances this year as she receives treatment for cancer. There is no evidence that Crooks had plans to travel to the UK.
Crooks’ interest in her was revealed as the FBI searched his two cell phones and one laptop.
On it they found he had searched for dates of Trump’s rally in Butler, Pennsylvania, where he ultimately made his assassination attempt.
There were also searches for the dates of the Democratic National Convention, investigators told a private briefing with lawmakers.
They also found photos of Biden and Trump in Crooks’ material.
FBI officials in the briefing said that that Crooks' search history indicated he had a strong interest in famous people, sources on the call confirmed to DailyMail.com.
The Princess of Wales was back in public at Wimbledon last Sunday - just hours after the assassination attempt on Donald Trump
Crooks was a dietary aide at Bethel Park Skilled Nursing and Rehabilitation Center - where he provided food and care for post-hospital elderly and sick people
In the aftermath of the assassination attempt of Mr Trump, King Charles wrote to the former president in a letter that was delivered by the British Embassy in Washington DC.
Charles survived his own assassination attempt in 1994.
The US Secret Service was facing serious questions last night about how a gunman managed to get close enough to shoot the former president.
Secret Service director Kimberly Cheatle has been summoned to testify before a committee of the US House of Representatives on July 22. She is facing calls to resign or face the sack.