Investigators in El Dorado County, California, have identified the same man as the killer of a young woman in 1977 and a teen girl in 1979 using an emerging DNA technique that relies on genealogy databases. The El Dorado County District Attorney’s office announced Monday that they partnered with Virginia-based Parabon NanoLabs to identify the killer of 27-year-old Brynn Rainey and 16-year-old Carol Andersen as Joseph Holt, a local real estate worker who died in 2014.

The decades-old murders of Rainey and Andersen near South Lake Tahoe are among the nearly 60 cold cases a county task force has been aiming to solve with the help of new forensic technology. The county of less than 190,000 has nearly double the amount of cases as counties twice its size, according to the district attorney’s office.

Since district attorney Vern Pierson established the task force in 2007, investigators have taken a fresh look at evidence, tracked down new leads and launched a video campaign in the hopes of publicizing the cases and generating tips. CBSNews.com featured both Rainey and Andersen’s stories as part of the campaign in 2015. The push resulted in “forward progress” on several cases, but the Rainey and Andersen cases remained unsolved until now, the district attorney’s office said.

The family expressed relief that the cases had been closed after so many years in statements released by the district attorney’s office.

“Finally, after 44 years of hell and back, we have some answers,” Rainey’s brother Pete Garl said.

Rainey was last seen on July 24, 1977, at a bar just before her 2 a.m. graveyard shift at the casino where she worked, just over the state line in Nevada. She had moved to South Lake Tahoe from Ohio just a few months before, and would often catch the bus or hitchhike to work. The next month, her nude body was found partially buried in a shallow grave in a horse riding area known as the Stateline Stables. Her cause of death couldn’t be determined because of decomposition, but a pathologist believed she was likely strangled or suffocated, according to the district attorney’s office.

Two years later, on June 30, 1979, Carol Andersen vanished on her way home from a party near a South Lake Tahoe ski resort. The Nevada teen’s battered body was found a few hours later on the side of a road about four miles away. Investigators said she had been strangled, and her wrists had marks indicating she had been bound.

Her sister Deanna Andersen told CBSNews.com in 2015 the rising high school junior suffered from epilepsy, and their mother rarely let her leave home by herself. Her mother had asked her not to go to the party the night she was slain, Anderson said.

Anderson said she is convinced her sister was targeted.

“She was so innocent,” said Deanna Andersen, who was 7 at the time of the murder. “She was just getting into the party scene.”

Holt lived about a six-minute walk from the home where Andersen was last seen, according to the district attorney’s office, and about a mile and a half from the location where Rainey was found slain. Both Rainey and Andersen’s family told investigators they had no indication that either knew Holt, a graduate of the University of California Berkeley who was 27 when he moved to South Lake Tahoe in 1974.

Investigators made a significant break in both cases in 2017 when they determined an unidentified male DNA profile from Andersen’s body matched a DNA profile from a blood stain found on Rainey’s shirt, indicating they had likely been killed by the same man. Investigators previously didn’t have evidence to link the two killings.

The profile, however, didn’t come up with a match in the FBI’s national criminal database. Investigators didn’t identify the suspect until  2018, after a Parabon genetic genealogist searched the DNA profile against genetic blueprints available on public genealogy databases. 

The technique that has gained popularity among law enforcement since it was used to identify “Golden State Killer” suspect Joseph DeAngelo, though it’s also raised a host of privacy concerns. It utilizes the public DNA databases, where users who have obtained their own DNA profiles from commercial companies such as Ancestry.com and 23andMe can upload them to expand their search for relatives.

The analysis led investigators to three deceased brothers they believed might be the source of the unidentified crime scene DNA,  one of whom was Holt, according to the district attorney’s office. Parabon’s genealogist built a “family tree” that investigators used to locate Holt’s son. The son provided investigators with his father’s toothbrush in Oct. 2018, and the match was confirmed in January.

Investigators executed a search warrant on Jan. 23 of a garage where Holt had stored some of his personal property, and uncovered “evidence suggestive of other criminal conduct,” according to the district attorney’s office. Investigators said they found a clipping of  a newspaper article from an unsolved 1975 shooting of a driver by a man who was burglarizing his car in Los Gatos.

The victim survived, and investigators were able to develop a suspect sketch that “strongly resembles” Holt in the mid-1970s, according to the El Dorado District Attorney’s office. In addition, the handgun was reported stolen from a cab driver in South Lake Tahoe. Investigators said Holt was known to frequent both South Lake Tahoe and Los Gatos.

In a statement, the El Dorado County District Attorney’s office said the task force is “honored and proud to bring resolution to both Brynn Rainey and Carol Andersen’s family after all these years.”

Investigators emphasized Holt’s family has been cooperative and were unaware of any allegations against him.

Speaking with CBSNews.com in 2015, relatives of both Andersen and Rainey said the murders were devastating for their families. Compounding their grief was a lack of answers about what happened to their loved ones. The families said that both of the victims’ mothers had died without knowing the identity of their daughters’ killer.

Now, they said, surviving family members have those answers.

“Almost 40 years ago, a beautiful, vibrant teenager was taken from her mother, older sisters, younger brother, and younger sister,” Andersen’s family said in a statement. “Unfortunately, relatively quickly the case went cold and while from time to time it would be revisited nothing could be found, until about a year ago. It was at that time that an incredible team of four investigators from the El Dorado County District Attorney’s Cold Case Files and through all their hard work and efforts, they were able to give the family some answers and closure and ultimately allow Carol Andersen to rest in peace.”