Washington shooting suspect took selfie before the attack

Moments before prosecutors say he tried to reach US President Donald Trump with a pump-action shotgun, the man at the centre of the case snapped a selfie inside his hotel room, documenting what authorities describe as a carefully staged attack.

Cole Allen allegedly moved into action shortly after 8.30pm on Saturday, leaving his room at the Washington Hilton and heading toward the basement ballroom, where Mr Trump and other senior officials were attending a media gala dinner, according to prosecutors.

The 31-year-old was wrestled to the ground and taken into custody after a frantic struggle with security personnel.

Gunfire erupted, but no one was killed.

A copy of the photo showed him wearing black clothing and a red tie, while carrying a knife, a shoulder holster for a handgun and what investigators identified as a bag for ammunition.

At the same time he left his room, scheduled emails were sent to friends and relatives containing a manifesto laying out his motives.

Secret Service agents responded after the shooting at the Washington Hilton

Those details, which prosecutors used to describe what they called an attack of “unfathomable malice”, were set out in a filing urging a Washington federal court to keep Mr Allen behind bars pending trial.

“The court should detain the defendant pending trial,” the filing said.

“The political nature of the defendant’s crimes further counsels in favor of detention because the defendant’s motivation for committing the crimes exists so long as he disagrees” with the government.

Mr Allen is described as a highly educated teacher from California.

Prosecutors said he travelled to Washington on a famously scenic train route through Chicago, bringing with him an arsenal that allegedly included the shotgun, a handgun and numerous knives.

During the trip, the filing said, Mr Allen noted his admiration for the passing scenery, writing on his phone that the woods of Pennsylvania looked like “vast fairy lands filled with tiny trickling creeks.”

After checking into the Hilton, he wrote that he was struck by what he viewed as weak security at the hotel, saying he had entered “with multiple weapons and not a single person there considers the possibility that I could be a threat”.

The shooting marked the third alleged assassination attempt against Donald Trump

In the emails sent to friends and family, prosecutors said, he listed members of the Trump administration as targets, ordered “prioritized from highest-ranking to lowest”.

He also wrote that he did not want Secret Service agents, other law enforcement officers or hotel guests to be killed.

According to the court filing, Mr Allen removed his long coat when he reached the hotel entrance area and then ran through one set of metal detectors with the shotgun ready.

He allegedly fired the weapon “in the direction of the stairs leading down to the ballroom”.

A Secret Service agent responded by firing five shots, none of which struck Mr Allen, who then fell and was subdued.

“The defendant suffered a minor injury to his knee but was not shot,” the filing said.

It was the third alleged assassination attempt against Mr Trump in less than two years.