After her 17-year-old daughter was found drowned in a shallow body of water, her waist-length red hair was cut off and a 100-lb. slumped over her body, Irene Avila comforted herself in the company of her daughter’s best friend, sharing their mutual pain.

The friend, Karen Severson, moved into Irene’s house, vowing to find the killer who had left Michele Avila alone in California’s Angeles National Forest in October 1985.

“She became like a daughter to me,” Irene told PEOPLE in a 1989 interview.

The two often stayed up talking about the beautiful, popular girl everyone called “Missy,” whose body was found by hikers two days after she got into a car with another friend, Laura Doyle.

Doyle had later claimed that he had left Missy with three boys driving a blue Camaro.

For the next three years, the only leads were false, and the case went cold.

Then another friend, Eva Chirumbolo, came forward, according to the facts of the case summarized by a judge in response to a writ of habeas corpus previously filed in the case.

Chirumbolo told investigators she was with the other girls when they headed into the national forest.

As it turned out, Doyle had recently broken up with her boyfriend – and she blamed Missy for it. The idea that Missy was to blame, PEOPLE previously reported, had come from Severson.

Walking through the woods, Doyle and Severson called Missy promiscuous, according to the filing, and Doyle grabbed her hair and cut off some of it. The two – who were taller and bigger than Avila, who weighed just 97 lbs. – then forced her into a shallow stream, tied her hands behind her back, dropped her and forced her head underwater until her body stopped.

Then, they left her pinned under a log heavier than her own weight.

In July 1988, Doyle and Severson were arrested in connection with Missy’s murder and were each later convicted of second-degree murder and sentenced to 15 years to life.

After years of mourning the loss of her daughter alongside her daughter’s killer, Irene began to see those first grief-stricken months differently.

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Severson had become obsessed with Missy’s case, visiting her grave several times a week and decorating her bedroom walls with pictures and newspaper clippings of her friend. He often took beer to the creek where Missy had been found, drinking at the crime scene.

She even said that Missy haunted her: she saw her dead friend sitting on the couch and even blamed her when her van wouldn’t start after a trip to the grave. – Miss, let me go! she screamed, according to the encounter described in PEOPLE’s previous coverage of the case.

Although Doyle had kept more distance from Irene, she had also occasionally stopped by to visit the grave, according to the filing, which adds that she “provided false leads” to investigators.

The California Parole Hearing Board later noted, according to the filing, that it was “particularly disturbing” that both women remained in such close contact with Missy’s family, even as they “kept a charade” about the fact that they didn’t know what happened to her. .

Both women have he has since been released. Severson was paroled in December 2011, and after 22 years behind bars, Doyle was paroled in July 2020.

Severson went on to publish a memoir about the murder, which led to the signing in 2015 of a Missy’s Lawwhich ensures that California convicts cannot profit from their crimes.

In a 1989 interview with PEOPLE, in which she maintained her innocence, Severson mentioned a boy she was interested in, claiming Missy had “moved into my territory” and said, “I couldn’t take it anymore. ”

But Missy’s family told PEOPLE at the time that it was more complicated than that. “She was Missy’s best friend,” Irene said, “but she was jealous of Missy’s family, Missy’s looks, Missy’s popularity, and even Missy’s relationship with me.”

Missy’s brother Mark added: “Karen wanted to be Missy.”