Gilgo Beach killings: Nassau prosecutors probing alleged serial killer Rex Heuermann's seized guns, court filing shows

Nassau County launched its own investigation into weapons possessed by accused Gilgo Beach serial killer Rex A. Heuermann after Suffolk prosecutors said they believe they seized dozens of unregistered handguns and assault weapons during the July search of his Massapequa Park home, a new court filing reveals.

The filing, a reply to Heuermann's opposition to send guns taken from his home to Nassau County, where he could face new criminal charges, notes that the Nassau County District Attorney's Office's Narcotics, Firearms and Guns Bureau launched its investigation Aug. 4.

"Several of the firearms were apparently illegally possessed," Assistant Suffolk County District Attorney Lawrence Opisso wrote in the motion filed Tuesday before state Supreme Court Justice Richard Ambro.

"For example, upon conversations with members of the Suffolk County Crime Lab and the Suffolk County Police Department, who recovered the items, but have not conducted a forensic examination, at least 26 unregistered handguns, 15 unregistered assault weapons and 10 high-capacity magazines appear to have been possessed in the defendant's home in violation of [state firearms laws]."

Opisso said Suffolk investigators indicated their intent to eventually transfer the weapons to Nassau County police when they filed their initial search warrant application July 13, the day he was arrested.

Heuermann filed court papers Sept. 21 opposing Suffolk's plan to turn over the more than 280 firearms seized from his home. His defense team instead urged the court to allow the weapons to be sold to benefit his financially struggling family.

Heuermann defense attorney Sabato Caponi argued that the court, which currently has possession of Heuermann’s weapons cache as well as “magazines, cases, attachments, ammunition, bullet fragments and shell casings," only transfer the weapons by law if Nassau County requests it or has a pending case involving the weapons.

Tuesday's court filing was the first public confirmation of a Nassau County investigation. The district attorney's office did not immediately respond to a request for comment.

Heuermann is facing multiple first- and second-degree murder charges in the killings of Megan Waterman, Melissa Barthelemy and Amber Lynn Costello, whose remains were found near Gilgo Beach 13 years ago, though prosecutors have said firearms were not used in those slayings. Heuermann has pleaded not guilty and remains held without bail at the Suffolk County Jail.

Prosecutors have said Heuermann, 60, who worked as a Manhattan architect before his arrest, is also the “prime suspect” in the slaying of Maureen Brainard-Barnes, whose remains were found with the other three victims. All four of the women — the first of 10 sets of remains found along Ocean Parkway that are believed to be the work of one or more serial killers — were sex workers.

Suffolk County Police Department detectives searched Heuermann’s Nassau County home for 12 days ending on July 26. Investigators also searched his Manhattan office, two units at a storage facility in Amityville and a Chevy Avalanche he used to own and which police seized from South Carolina.

An inventory of the weapons seized showed that he had collected many guns from the early part of the last century, and his collection also included assault rifles, and a rifle with a defaced serial number, according to court documents.

Prosecutors have said Heuermann had permits for 92 guns and possessed many long guns not subject to permitting. His pistol license was suspended by Nassau County following his arrest, prosecutors have said.

Heuermann's lead defense attorney, Michael Brown of Central Islip, could not be immediately reached for comment. Heuermann is due back in court Nov. 15.

By Grant Parpan

grant.parpan@newsday.com@GrantParpan

Grant Parpan covers Suffolk County courts and federal courts for Newsday. A Long Island native, he joined Newsday in 2022.