Cole Tomas Allen pleaded not guilty in federal court to charges that he attempted to assassinate President Donald Trump during an armed attack at a White House Correspondents’ Association event in Washington, D.C.

Prosecutors say Allen, armed with a shotgun, knives, and other gear, fired at a Secret Service officer who confronted him after he breached security at the Washington Hilton hotel.

The attack injured a Secret Service officer and briefly disrupted the high-profile political dinner before Allen was subdued and taken into custody.

His defense team is seeking to disqualify senior Justice Department officials from the case, arguing a potential conflict of interest because they were present at the event, the AP has reported.

Allen faces multiple charges, including attempted assassination of the president, and could receive a life sentence if convicted.