Mark Mazza on January 6, 2021.
CNN  — 

A January 6, 2021, rioter pleaded guilty Friday to carrying a loaded firearm on US Capitol grounds and assaulting police officers with one of their own batons during the insurrection.

Mark Mazza, who told federal investigators he regretted not seeing House Speaker Nancy Pelosi during the riot and that they would “be here for another reason” if he had, faces a maximum of 20 years for assaulting officers with a dangerous weapon.

According to the plea agreement, Mazza, 57, carried a revolver loaded with shotgun and hollow-point rounds in a holster under his shirt during the “Stop the Steal” rally and on Capitol grounds that day.

Republican lawmakers and conservative allies have often falsely claimed that no weapons were brought to the Capitol to argue the attack was not the violent insurrection that it was.

Mazza lost the weapon on Capitol grounds sometime before walking to the Lower West Terrace tunnel where rioters were battling police officers, according to the plea.

Inside the tunnel, Mazza held open a door against police officers as “other rioters used flag poles, batons, sticks, and stolen law enforcement shields as weapons to strike at, hit, and try to force their way through” the police line, the plea agreement states.

He then stole a police officer’s baton and used it against the officers guarding the tunnel entrance.

The plea agreement also states that after Mazza was pushed out of the tunnel by police officers, he “took steps to assist” Capitol Police Officer Michael Fanone, who was dragged out into the crowd and beaten. Mazza, the agreement says, “was in close physical proximity to (Fanone) and took steps to assist the officer from being further assaulted by members of the riot.”

Mazza left Capitol grounds only after law enforcement deployed flash-bang grenades later that day, the agreement says.

Mazza originally denied assaulting officers, even saying he assisted them out of the building, despite video footage of him swinging a baton in a battle with police. He drove home to Indiana after the riot with the stolen baton in his possession, according to prosecutors.

Mazza was recorded in multiple videos saying, “We own this house!”

Federal investigators found Mazza after he falsely reported the weapon he brought to the riot was stolen on January 8, 2021, claiming it was taken from his car at an Ohio casino. He later told investigators he fabricated the claim because he feared member of Antifa might find the gun and his name was “all over it.”

This story has been updated with additional information Friday.