WASHINGTON (AP) — A man accused of storming the White House Correspondents' Association dinner while armed with guns and knives pleaded not guilty on Monday to charges that he attempted to kill President Donald Trump and fired a shotgun at a Secret Service officer who tried to stop the attack.

WATCH: New video of Correspondents' Dinner shooting raises questions about presidential security

Cole Tomas Allen was handcuffed and shackled and wearing an orange jail uniform when he appeared in federal court for his arraignment. Allen didn't speak during the brief hearing. One of his attorneys entered the plea on his behalf.

Allen's lawyers are asking U.S. District Judge Trevor McFadden to disqualify at least two top Justice Department officials from direct involvement in prosecuting him because they could be considered victims or witnesses in the case, creating a potential conflict of interest.

Acting Attorney General Todd Blanche and U.S. Attorney Jeanine Pirro were attending the event when Allen ran through a security checkpoint and fired a shotgun at a Secret Service officer, authorities said. In a court filing last week, Allen's attorneys argued that it creates at least the appearance of a conflict of interest for Blanche and Pirro to be making any prosecutorial decisions in the case.

McFadden, a Trump nominee, didn't rule from the bench on that question but asked Allen's attorneys to elaborate on the possible scope of their recusal request. Defense attorney Eugene Ohm said the defense likely would seek to disqualify Pirro's entire office from involvement in the case. Ohm acknowledged that a bid to disqualify the entire Justice Department would be unlikely.

"That would be quite a request," the judge said.

McFadden gave prosecutors until May 22 to respond in writing to the defense's request. The judge asked the government to specify whether it believes Pirro and Blanche could be considered victims in the case.

"That might add some clarity here," McFadden said.

In their filing, Allen's attorneys suggested that the appointment of a special prosecutor might be warranted.

Allen is scheduled to return to court on June 29.

A Secret Service officer was shot once in a bullet-resistant vest during the April 25 attack at the Washington Hilton hotel, which disrupted and ultimately prompted an early end to one of the highest-profile annual events in the nation's capital. The officer fired five shots but didn't hit anybody, authorities said.

Allen, 31, of Torrance, California, was injured but was not shot.

Besides the attempted-assassination count, Allen also is charged with assaulting a federal officer with a deadly weapon and two additional firearms counts. He faces a maximum sentence of life in prison if convicted of the attempted assassination charge alone.

Allen was placed on suicide watch after his arrest, but jail officials removed him from that status after several days. Allen's attorneys complained that he had been unnecessarily confined in a padded room with constant lighting, repeatedly strip searched and placed in restraints outside his cell.

Allen told FBI agents that he didn't expect to survive the attack, which could help explain why he was deemed to be a possible suicide risk, a Justice Department prosecutor has said.

Allen was outfitted with an ammunition bag, a shoulder gun holster and a sheathed knife when he took a photo of himself in his room at the hotel just minutes before the attack, according to prosecutors. In a message that authorities say sheds light on his motive, Allen referred to himself as a "Friendly Federal Assassin" and alluded obliquely to grievances over a range of actions by Trump's Republican administration.

Authorities have alleged that Allen on April 6 reserved a room for himself at the Hilton where the event would be held weeks later under its typical tight security. He traveled by train cross-country from California, checking himself into the hotel a day before the dinner with a room reserved for the weekend.

Trump was rushed off the stage by his security team at the Saturday night event and appeared at the White House two hours later, still in his tuxedo, to talk about the attack and the suspect.

"When you're impactful, they go after you. When you're not impactful, they leave you alone," the president said. "They seem to think he was a lone wolf."