Cole Tomas Allen, the suspected gunman at the White House correspondents’ dinner, is facing an additional related charge for assaulting a federal officer with a deadly weapon, federal authorities announced on Tuesday.

The new charge, which formally accuses Allen of firing at a US Secret Service agent at a security checkpoint, is part of a new four-count indictment returned by a federal grand jury in Washington. The other three counts are charges Allen previously faced: attempted assassination, discharge of a firearm during a crime of violence and illegal transportation of a firearm and ammunition across state lines.

On 25 April, Allen, a 31-year-old California man, allegedly sprinted past a security checkpoint at the Washington Hilton hotel, where the annual press gala was taking place.

Prosecutors allege Allen was running toward the hotel’s ballroom with the intent to assassinate Donald Trump and other senior administration officials, who were dining with roughly 2,500 journalists and other guests.

In Tuesday’s announcement, federal prosecutors claimed that as Allen rushed the security perimeter, he fired a shotgun and hit a Secret Service agent in the chest.

Several other weapons were found in his possession, prosecutors said.

“Today’s indictment underscores a simple truth: there is evidence this defendant intended to assassinate the president, and that he shot a US Secret Service officer after he traversed the country with a cache of ammunition to accomplish his goals,” the US attorney for the District of Columbia, Jeanine Pirro, said on Tuesday. “The use of violence to register dissent is anti-democratic at its core. We will pursue the maximum punishment available under the law against anyone who travels to the District of Columbia to engage in such acts.

“As alleged in today’s indictment, the heavily armed defendant rushed security and shot a Secret Service Officer in an attempt to assassinate President Trump – but was stopped thanks to the courageous and immediate response from law enforcement,” said the acting attorney general, Todd Blanche.

The the initial set of charges against Allen did not accuse him of shooting the agent, nor was it mentioned in a court document prosecutors filed on 29 April seeking Allen’s detention.

Pirro released video of the moment Allen charged the security checkpoint last Thursday, claiming the footage showed Allen shooting the Secret Service agent. Pirro told CNN in an interview on Sunday that a pellet that came from Allen’s shotgun recovered at the scene was intertwined with fibers from the vest of the agent.

The agent, who was wearing a bulletproof vest, was not seriously injured.

Reuters contributed