One of the most notorious serial murderers and a suspected victim found near Green River, Wyoming, are the subject of a recent television documentary.

ABC's 20-20 on Jan. 8 featured Rodney James Alcala, known as "The Dating Game Killer," on a recent show and started with the story of his killing a Texas woman in 1977.

Alcala was known as "The Dating Game Killer" because he appeared as a contestant of the popular television show in 1978, was charged and convicted of murdering two women in New York crimes in 2012 and given a lengthy prison sentence before being returned to California where he is on death row for murders committed in that state.

He also murdered San Antonio resident Christine Ruth Thornton, 27, and disposed her body in a remote area northeast of Granger, a small community northwest of Green River.

Among those interviewed on the 20-20 episode was Chris Thorton's sister.

Kathy Thornton and others said her sister was trusting, had met up with her boyfriend "and had this crazy idea to go to Montana to pan for gold." They were in southwest Wyoming, they had an argument and split up, and left her pregnant and alone.

Chris Thornton went missing in 1977.

Kathy Thornton said she went to San Antonio in 1978 and wanted to file a missing person's report with the San Antonio Police Department, but it would not accept the report because Chris was an adult.

In 1982, a local rancher found her remains and the bones of an infant. There was no identification with the remains, according to those interviewed on 20-20.

Meanwhile the Huntington Beach, Calif., Police Department made public photographs found in Alcala’s possession in 1979. In 2013, a relative of Thornton saw the photographs and found one of Chris Thornton, and her family contacted the police department.

Enter your number to get our free mobile app

In 2013, Sweetwater County Sheriff's Office detective Jeff Sheaman opened the cold case and submitted a tissue sample from the remains to the University of North Texas Center for Human Identification for mitochondrial DNA analysis and inclusion into the National Missing and Unidentified Persons System (NamUS).

In 2014, two of Thornton’s siblings submitted their DNA samples for inclusion into the NamUS system, and the following year NamUS contacted Sweetwater County detectives about the possible identification of Thornton.

Detectives with the help of the Wyoming Crime Lab positively identified Thornton's remains. Detectives determined the photograph of Thornton was taken a short distance from where her remains were found.

In September 2016, Sweetwater County officials filed charges against Alcala.

Authorities don’t know the full extent of his crimes. They estimate he may have up to 130 victims across the United States.

NEXT UP: 10 Absolute WORST Tourist Incidents at Yellowstone National Park