The prosecution submitted the photos along with new details about the suspect's activities before the April 25 incident, as part of a request to keep Allen in custody until trial.
The 31-year-old has pleaded not guilty to multiple charges, the BBC reports, including attempting to assassinate the president. Donald Trump.
Prosecutors allege that the photos show Allen in his hotel room posing in front of a mirror with multiple weapons strapped to his body, including a knife in a holster, as well as a bag of ammunition.
Justice Department photos show Cole Allen posing in front of a mirror with multiple weapons.
Allen is accused of carrying a semi-automatic pistol, the BBC reports, a pump-action shotgun and three knives when he walked past security at the White House Correspondents' Association dinner on Saturday.
During the incident on Saturday night, Trump, Vice President JD Vance, Cabinet members and other White House officials were evacuated from a ballroom at the Washington Hilton Hotel after shots rang out.
One Secret Service agent was wounded, but not seriously. Allen faces life in prison if convicted.
In the new memorandum, prosecutors allege that Allen took a photo of himself in a hotel room on a cellphone, dressed in formal attire, with a gun holster over his shoulder, pliers and wire cutters, which were later found on him.
The government claims that for the next half hour, Allen checked multiple websites to watch the live broadcast of the White House Correspondents' Dinner and the President's presence. Then he headed downstairs to the room where the dinner was being held, the BBC reports.
Prosecutors allege that Allen was wearing a long black coat that concealed a pump gun.
According to the government, he ran through a metal detector with the rifle held in both hands in a raised position. The new filing also alleges that Allen kept notes on his phone of his observations during the trip from his home in California to Washington.
Prosecutors argue that Allen should remain in custody until trial, saying his alleged actions were "premeditated, violent and designed to cause death."
