HERNANDO COUNTY, Fla. (WFLA) — Hernando County deputies are providing more insight into how they were able to identify the remains of a victim in a case that went cold more than 40 years ago.

Family members told WFLA on Tuesday they were notified that the remains of Theresa Caroline Fillingim, a teenager who went missing in 1980, had been found at the home of convicted serial killer Billy Mansfield Jr.

Authorities confirmed the identification in a news conference on Wednesday. They said four sets of human remains were recovered from the Mansfield’s Hernando County property in March and April of 1981. Two of the victims were immediately identified, however, two other victims remained unidentified — until now.

Cold case detectives, working in conjunction with the University of North Texas and Parabon Nano Labs, used the company’s “Snapshot DNA Phenotyping Service” to narrow the list of suspects and victims to generate leads.

Using DNA evidence collected from the burial site, the DNA Snapshot predicted the victim’s ancestry, eye color, hair color, skin color, freckling, and face shape. This profile was then used by investigators to identify the victim, the sheriff’s office said.

Investigators then determined that Theresa Caroline Fillingim was in fact one of the two unidentified victims in the cold case investigation.

“It gives me peace because I know I didn’t lose her,” one family member told News Channel 8. “That she was taken.”

Mansfield’s murders came to light after he raped and strangled René Saling in 1980. Mansfield then dumped the body of the mother of three in a ditch near a campground where he was staying with his brother, Gary Mansfield.

While authorities in California were investigating Saling’s murder, Hernando County authorities discovered four bodies at Mansfield’s family home in Spring Hill, each in different stages of decomposition.

The sheriff’s office said it will “continue to use evolving technology and investigative techniques as appropriate to help solve violent crimes” in the future.