A serial killer convicted of the murders of 12 women has confessed to the cold case murder of a 19-year-old mother in Southern California in 1986. 

Cathy Small, 19, was found stabbed to death on a street in South Pasadena in February 1986, but her case went unsolved for nearly four decades. 

"We believe we’re bringing a sense of long overdue justice and closure to the victim and her family," Los Angeles County Sheriff Robert Luna said in a press conference this week. 

William Lester Suff, known as the "Lake Elsinore Killer" and the "Riverside Prostitute Killer" admitted in 2022 to murdering Small after his DNA was found on her clothing, saying she "enraged" him by knocking his glasses off his face during a fight, Lt. Patricia Thomas said during Tuesday's briefing. 

SUSPECT, 78, CHARGED IN 44-YEAR-OLD COLD CASE KIDNAPPING, MURDER OF NURSING STUDENT

A split of Bill Suff and Cathy Small

A serial killer convicted for the murders of 12 women confessed to the cold-case murder of a 19-year-old mother in Southern California in 1986.  (Los Angeles County Sheriff's Department)

Suff told investigators Small had first met him at a computer repair shop where he worked and agreed to drive with him from Lake Elsinore in South Pasadena for $50.

After he stabbed her repeatedly in the passenger seat of his car, he admitted to tossing her body on the sidewalk and driving away, Thomas said. 

Suff, who is on death row at San Quentin in California, also admitted to other unsolved cold case murders in Riverside County, Thomas said, but didn’t identify the victims. 

Investigators realized DNA collected from the crime hadn't been tested, and, when it was, Suff’s DNA was found on her clothing. 

Suff began killing in the 1970s and was convicted in the death of his 2-month-old daughter in Texas in 1974 and sentenced to 70 years, but he was paroled in 1984 and moved back to California. 

Photos of Kathy Small with her children

Cathy Small, 19, was a mother of two young children when she was killed.  (Los Angeles County Sheriff's Department)

Luna said Suff’s confession underscores "the power of modern forensic science; two, the amazing, relentless work by our Los Angeles homicide bureau detectives, which I keep on saying are the best in the country at what they do; and then the collaboration and partnership between agencies.

AUTHORITIES SEEK PUBLIC'S HELP IDENTIFYING SUSPECTED TEXAS SERIAL KILLER AFTER DNA LINKS PERSON TO 2 MURDERS

"Amongst everything else we’re talking about today, you always got to remember when we’re talking about something as significant as this, we’re talking about a victim who lost her life and the family who will never forget that. And I know we never forget that, and that’s what makes the teamwork here so amazing." 

Thomas also read a letter written by Small’s younger sister, who was 10 at the time of her murder but couldn’t be at the news conference because she lives out of state.

"My sister Cathy Small was not a statistic," she wrote. "She was a protective big sister, a loving mother and a good daughter. Cathy was funny, smart and caring. She had a big heart and would do anything for anyone."

Photos of Bill Suff

William Lester Suff is a serial killer on death row for the murders of 12 women. (Los Angeles County Sheriff's Department)

Small’s sister said the 19-year-old taught her how to swim, ride a bike and play cards. 

"Whenever I stayed with my big sister, she took me to church," she continued. "Cathy was talented, but her life was cut short before she could even begin to make her own dreams come true."

She added that Small, who was working as a sex worker at the time of her murder, was trying to get sober and had stopped using drugs, "but before she could take another step forward her life was ended." 

CLICK HERE TO GET THE FOX NEWS APP

She added that she is "forever indebted" to the Los Angeles County Sheriff’s Department "for making sure the memory of my sister Cathy Small stayed alive despite her senseless murder more than 35 years ago in February of 1986. The man who murdered my sister also destroyed me, my family and the families of others. … I will always miss my sister Cathy. 

"Nothing will bring her back. Bill Suff is where he’s supposed to be, and he can no longer hurt anyone. Thank you for remembering my sister Cathy."