The man charged with trying to storm the White House Correspondents’ Association dinner and kill US President Donald Trump took a picture of himself in his hotel room just minutes earlier, outfitted with an ammunition bag, a shoulder gun holster and a sheathed knife, authorities said on Wednesday in a new court filing.

Cole Allen wore black pants, a black shirt and a red tie as he snapped the image in his room at the Washington Hilton, where Trump and hundreds of journalists were meeting for a gala Saturday night, authorities say.

The 31-year-old from Torrance, California, was captured when he tried to race past security barricades near the hotel’s ballroom, prompting an exchange of gunfire with Secret Service agents tasked with safeguarding the event, investigators say.

New details emerged in a court filing made by prosecutors who want Allen to remain in custody. A hearing is set for Thursday.

The government said Allen repeatedly made online checks to keep track of Trump’s status that night, including live coverage of the president exiting his vehicle at the Hilton hotel. Investigators said preset emails with an “Apology and Explanation” attachment were sent at around 8.30pm.

“He intended to kill and fired his shotgun while trying to breach security and attack his target. Put simply, the defendant poses an uncommonly serious danger to the community if released pending trial.