The suspect in the attack at the White House Correspondents’ Dinner on Saturday night was prepared for a mass casualty event, prosecutors said in a document filed in federal court early Wednesday.

Jeanine Pirro, the U.S. attorney for the District of Columbia, and three assistants in her office signed a memorandum asking a judge to keep 31-year-old Cole Tomas Allen detained as he awaits trial. They said his “actions were premeditated, violent, and calculated to cause death,” and he sought to “express his political opinions through violence.”

“Had the defendant achieved his intended outcome, he would have brought about one of the darkest days in American history,” they wrote. “The defendant traveled across the country with the explicit aim to kill the President of the United States.”

A detention hearing is set for Thursday. Allen is charged with attempting to assassinate President Donald Trump, as well as interstate transportation of a firearm with intent to commit a felony and discharge of a firearm during a crime of violence.

He faces up to life in prison if convicted of attempting to kill the president. Trump, first lady Melania Trump and Cabinet members all safely evacuated the Washington Hilton ballroom.

The document lists a host of weapons, ammunition and other supplies Allen had in his possession at the time of his arrest.

He had a “12-gauge pumpaction shotgun with one spent cartridge in the barrel and eight unfired cartridges in the magazine tube,” the document reads. He carried additional ammunition in a Velcro strapped to his body and in a separate pouch, the prosecutors said. 

He also carried a fully loaded .38 caliber pistol with two additional magazines. 

The document also shows a mirror selfie Allen appears to have taken in his hotel room just before the planned attack. He is fully armed and outfitted in the photo.

The White House Correspondents’ Dinner, dating back more than 100 years, is an annual black-tie event, often attended by the president, that hosts more than 2,000 journalists, administration officials and other guests at the Washington Hilton. 

President Donald Trump, Vice President JD Vance, House Speaker Mike Johnson, R-La., and members of the Cabinet attended Saturday’s dinner, along with many members of Congress. 

Allen, who traveled by train from Los Angeles to Washington, D.C., prior to the attack, sent a note just prior to attempting to rush the Capital Hilton ballroom, brandishing a gun. 

He did not name Trump but said, “Administration officials (not including Mr. Patel): they are targets, prioritized from highest-ranking to lowest.”

Prosecutors argued his intent was to inflict mass harm and disrupt the government.

“Had the defendant successfully made it into the ballroom, he not only could have killed or injured dozens of people, but he could have destabilized the entire federal government, given the number of high-ranking government officials present,” the Department of Justice said. “The defendant sought to express his political opinions through violence. The Court should consider the identities of the defendant’s intended victims and the significant roles they play in governing this country to assess the nature of the charged offenses.”