On Dec. 20, 1984, Jonelle Matthews performed at a Christmas concert at Franklin Middle School in Greeley, Colo., singing “Jingle Bells” with fellow members of the Honor Choir.

After the concert, a friend’s father dropped the 12-year-old off at her house at about 8 p.m. But no one was home. Her mother was out of state, caring for Jonelle’s grandmother, who was sick, and her father was at her older sister’s basketball game.

When Jonelle’s father, Jim Matthews, returned home that night, Jonelle wasn’t there.

That night, police found footprints in the snow near the windows of the house, which someone had tried to blur with a garden rake, Jim Matthews told 48 Hours.

Jonelle was never seen again.

For decades, her devastated family wondered what happened to the sweet 7th grader, whose disappearance cast a pall over Greeley.

On Monday, a jury found Steven Pankey, 71, guilty of felony murder and second-degree kidnapping, the Weld County Prosecutor’s Office announced in a statement.

A former Greeley resident, Pankey later moved to Idaho where he undertook two unsuccessful runs for governor in 2014 and 2018.

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Shortly afterward, District Court Judge Timothy Kerns sentenced Pankey to life in prison with the possibility of parole, the Greeley Tribune reports.

“I just want to cry,” Jonelle’s mother, Gloria Matthews said afterward, The New York Times reports.

“God is the only one who can forgive evil, and I feel that this is evil.”

Jennifer Mogensen, says she wishes she could have grown up with her little sister, Jonelle, who noted that 12,634 days had gone by since Jonelle vanished, the Greeley Tribune reports.

“My husband never met his sister-in-law, and my son never met his aunt,” Mogensen said.

For years, the case went cold until July 2019, when oil and gas workers dug up Jonelle’s remains in an unincorporated part of Weld County.

Already a person of interest, Pankey was arrested in October 2020 after a grand jury indicted him on charges of murder, kidnapping and false reporting, the Greeley Tribune reported.

The October 9, 2020, indictment against Pankey alleged that “he took Jonelle Matthews from her family home …” and “shot Jonelle Matthews during the course of the kidnapping,” 48 Hours reports.

Anthony Viorst, Pankey’s defense attorney at the time, told 48 Hours that his client is innocent. “There’s no indication that he committed this murder, no indication that he had anything to do with burying the body,” Viorst said.

The indictment said that Pankey knew about a rake that was used to blur footprints in the snow the night Jonelle vanished, 48 Hours reports.

In Oct. 2021, he was tried in the case, which ended in a mistrial after the jury could not reach a unanimous verdict on the murder and kidnapping charges.

The jury found him guilty of false reporting in 2021.

Pankey’s attorney did not immediately respond to PEOPLE’s request for comment.