A 67-year-old man was convicted Thursday of raping and killing two women in the 1980s and officials said it was the first case in Los Angeles County that used investigative genetic genealogy.

Jurors found Horace Van Vaultz guilty of two counts of first-degree murder with special circumstance allegations of multiple murders and that the crimes were committed during a rape and sodomy for each victim.

Van Vaultz killed 22-year-old Mary Duggan on June 9, 1986, officials said. The victim was found in the trunk of her car in an empty parking lot in Burbank. She was bound, sexually assaulted and died from asphyxia because a tissue was stuffed down her throat, officials had previously detailed.

He was also convicted of killing 20-year-old Selena Keough on July 1981 in Montclair. She was found in bushes and had also been bound, sexually assaulted and strangled.

Investigators had previously reached out to other law enforcement agencies to determine if Van Vaultz was responsible for other unsolved murders in the state.

Officials did not elaborate on how they were able to identify Van Vaultz as the killer, but indicated the cases were investigated by the Burbank and Montclair police departments, along with the FBI’s Genetic Genealogy Team.

Van Vaultz was charged in connection with the decades-old crimes in November 2019.

He is scheduled to be sentenced on Sept. 19.

“Using the latest in technology and forensics, we were able to secure a conviction against someone who targeted young women,” L.A. County District Attorney George Gascón said. “I hope that today’s guilty verdict provides some comfort to the victims’ families who have waited more than three decades to see this result.”