The 60-year-old was first arrested in July 2023 for the deaths of four women whose remains were found in burlap sacks along the Ocean Parkway in New York over a decade ago.
Detectives finally nabbed Heuermann in 2023 after he tossed a pizza box with leftover crust into a Manhattan trash can after the investigation that took more than a decade. The DNA from his crust matched genetic material found on the women's remains.
Heuermann faces charges in connection to the murders of Melissa Barthelemy, Megan Waterman, Amber Lynn Costello and Maureen Brainard-Barnes - also known as "The Gilgo Four." Taylor and Costilla were announced has Heuermann's fifth and sixth victims on Thursday.
The announcement comes weeks after authorities returned to Heuermann's Long Island home. At least half a dozen law enforcement agents were spotted in Heuermann's driveway on May 20.
Heuermann is currently being held at the Riverhead Correctional Facility in Suffolk County, about 50 miles from his home.
Suffolk County Sheriff Dr. Errol Toulon Jr. said Heuermann busies himself with reading books, reading his discovery, watching TV and sleeping, according to an Oxygen article.
He has been separated from other inmates "for his safety," according to the article. Toulon called him "very compliant."