Gilgo Beach murders: Sources say Rex Heuermann is charged with the 2000 murder of New Jersey woman Valerie Mack

RIVERHEAD, New York – Accused Gilgo Beach serial killer Rex Heuermann is charged with a seventh murder, law enforcement sources told ABC News.

Officials charged Heuermann with the murder of Valerie Mack, a New Jersey woman whose remains were discovered in November 2000.

He is scheduled to be arraigned Tuesday in Suffolk County court on a supplemental indictment that includes a new charge of second-degree murder.

RELATED: The prosecutor says the office lacks the resources to meet the judge’s “ambitious” deadlines in the Gilgo Beach case

Mack’s parents are expected to attend a news conference as prosecutors announce the new charges.

Mack, once known as Jane Doe Number 6, was found on a wooded lot on Mill Road west of Halsey Manor Road in Manorville. She was identified four years ago using DNA from her remains.

Like the other women, prosecutors said she was also involved in sex work.

Suffolk County District Attorney Ray Tierney named Heuermann the prime suspect in her death during a news conference in June. Her family was told to expect developments by the end of the year.

The architect and father has pleaded not guilty to charges related to the murders of six women whose remains were found at a remote location on Ocean Parkway near Gilgo Beach and parts of eastern Long Island

Prosecutors named Heuermann a suspect in Mack’s death in June based on evidence that allegedly included an electronic device seized from Heuermann’s Massapequa Park home. Prosecutors said Heuermann kept detailed records of serial killings, body disposal and torture pornography.

A spokeswoman for Tierney declined to comment.

Heuermann, 61, is scheduled to appear in court at 9:30 a.m. in Riverhead

The Suffolk County District Attorney’s Office scheduled a news conference along with local and state law enforcement following Heuermann’s morning court appearance, but did not provide details on what the announcement of the development would entail.

In addition to Mack, prosecutors are also investigating the death of Karen Vergata, whose remains were first discovered in 1996 and finally identified in 2022 after new DNA analysis.

In September, authorities released new accounts of an unidentified victim found in 2011. Officials said the victim, whom they had identified as male for years, may have been masquerading as female and died in 2006.

Heuermann was initially charged with the deaths of three women in 2023, and was charged with three others earlier this year. In the complaint accompanying the latest charges, prosecutors said they had recovered a file on a hard drive in Heuermann’s basement that he used to “methodically plan” his murders – including checklists of tasks to complete before, during and after Lessons for “next time.”

Some information from ABC News and Associated Press