WASHINGTON (AP) — A Marine detailed to the office of California GOP Rep. Duncan Hunter Jr. was arrested Tuesday for possession of an unregistered firearm after a loaded .45 caliber handgun was discovered in his vehicle.

Gunnery Sgt. Peter Boby, a congressional fellow in the Corps' Office of Legislative Affairs, was arrested after being stopped at a security checkpoint near a House office building, according to the U.S. Capitol Police.

Boby was also charged with carrying a pistol without a license and possession of unregistered ammunition. He processed at Capitol Police headquarters.

Hunter issued a statement Tuesday evening calling Boby "a top-notch performer."

"He's a hero who's seen combat, who's been wounded and who's been in good standing with the Marine Corps throughout," Hunter said. "We are still getting the facts but this was most likely an accident. There's no reason to suggest it was intentional."

Congressional fellows remain employees of the Pentagon and are dispatched to Capitol Hill offices, where they assist lawmakers and broaden their work experience.