The gunman who attempted to kill Donald Trump researched a member of the Royal Family as he planned targets for assassination, the FBI has revealed.

FBI investigators revealed to members of Congress that Thomas Crooks,20, went online to "scope out" a number of potential high-profile assassination targets - which included an unnamed member of the Firm.

US security authorities have launched an investigation into the shooting, which almost killed Trump.

The Republican candidate dodged a bullet that whizzed past his head, clipping and injuring his ear.

Investigators also discovered that Crooks' devices contained images of President Joe Biden and Mr Trump, as well as the dates of both rallies and the Democratic National Convention, which are due to take place in Chicago next month.

Crooks also searched for Christopher Wray, the director of the FBI, and Merrick Garland, the US Attorney General.

US senators were told the 20-year-old killer posted on the gaming network Steam: 'July 13 will be my premiere, watch as it unfolds.'

The shooting appeared to be planned just days in advance, as Crooks went to a local club the day before and practised on the rifle range, according to a federal intelligence briefing.

On the day of the attack, he purchased 50 rounds of 5.56mm ammo for his rifle from a local gun shop and drove alone to Butler, Pennsylvania, the site of the Trump rally.

Crooks worked at a nursing home as a dietary aide, sources have claimed he asked his employer to take the day off on the day of the shooting but said he would be back as soon as the next day.

Marcie Grimm, the administrator of Bethel Park Skilled Nursing and Rehabilitation, said in a statement she was “shocked and saddened to learn of his involvement.” Ms Grimm added that Crooks had a clean background check when he was hired.

It is unclear what the motive is behind Crook's attack, based on state voting records, Crooks was a registered Republican voter.

The FBI said it believes Crooks, who had bomb-making materials in the car he drove to the rally, acted alone and has been labelled a "lone wolf".

A blockade remains in place near Crooks’ house, about an hour's drive from the site of the Trump rally.

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