Groton — A Groton man police arrested in May after he had barricaded himself in his home faces a host of weapons charges after police on Friday announced they had seized several unregistered guns and high-capacity magazines at his residence.

Robert J. Patterson, 52, of 17 Fleming Court was arrested the morning of May 25 after his estranged girlfriend told police he was heavily armed and being irrational, police said. Police at the time said Patterson indicated he wanted "death by cop."

On Friday, police announced they had siezed a silver revolver with a cut barrel and no identifiable serial number; an Intratec Tec-22 semi-automatic handgun with a silencer; an AK-47 rifle; two banker boxes of ammunition; and 14 various high-capacity magazines. None of the items was registered through the Connecticut Firearms Unit, police said.

Patterson was charged with two counts of possession of an assault weapon, alteration of a firearm identification number, possession of a silencer and 14 counts of possession of large-capacity magazines. He pleaded not guilty.

Patterson is held on a total of $250,000 bond, police said.

He already had pleaded not guilty to first-degree reckless endangerment, breach of peace, second-degree strangulation, disorderly conduct and third-degree criminal mischief stemming from the May 25 arrest.

Officers that morning set up a perimeter around Patterson's house, closing a portion of Mitchell Street and asking residents to shelter in place via a reverse 911 alert. Police evacuated nearby residences as a precaution.

Town police and members of the state police Emergency Services Unit assisted city police. A state police hostage negotiator worked with Patterson for several hours until he surrendered.

Patterson is due back July 26 in New London Superior Court.

Anyone with information related to criminal activity is encouraged to call the Groton City police in-house dispatch at (860) 445-2451.