The failed gubernatorial candidate who was dubbed the "Girl on the milk carton" killer is being described as a "monster" who "taunted" police.

Since 1984, the case of Jonelle Matthews, a seventh-grader who disappeared five days before Christmas, has always intrigued Steve Pankey.

It would take over three decades for the police to find out why.

"Retired lead detective Robert Cash revealed to Planet Chronicle Digital that the suspect was a monster who taunted law enforcement. However, after analyzing the evidence, it became clear that the suspect's behavior and writings indicated that his taunting was a way to gain satisfaction from duping law enforcement."

"He was a monster who tapped on the shoulder of law enforcement."

"He kept the case alive through his consistent hint-dropping and rehashing," Cash stated. "Fortunately, he hit the right person at the right moment."

The investigation into the case of the 12-year-old Greeley, Colorado, resident is being explored in a two-part special on Oxygen, "The Girl on the Milk Carton." The special features new interviews with Matthews' family, local police who investigated for almost 40 years, as well as Angela Hicks, Pankey's ex-wife.

The documentary also details how Hicks played a role in solving the case.

"Before conducting any interviews, Hicks felt that the documentaries and true-crime podcasts he was watching were inaccurate. He wanted to create a documentary that would honor Jonelle Matthews."

Matthews, a member of the Franklin Middle School Honor Choir and active at the Sunny View Church of the Nazarene, was taken home by a friend and the friend's father after performing at a Christmas concert with classmates. Her mother was out of state caring for her ailing grandmother, and her father was at her sister's basketball game.

On Dec. 20, at 8 p.m., Matthews entered her family's lit ranch-style home with a detached garage, the front yard covered in snow.

At the time of their marriage, Hicks described their impromptu trip to California and how they left Big Bear Lake abruptly upon learning of Matthews' disappearance.

"Hicks remembered the day they were driving and Steve said, "Turn the radio on." It was unusual because Steve had banned radio, TV, and newspapers a year earlier. They didn't have any of that in their lives. Hicks assumed Steve wanted to listen to some old '50s rock 'n' roll, but Steve said no. He wanted to hear the news channels. That's when Hicks heard about Jonelle Matthews' disappearance."

"While driving on Christmas Day and the following day until we returned to Greeley, Hicks was fixated on finding news about the missing girl. He constantly flipped the radio, searching for updates. The mention of Sunny View Church, where Steve was a member, piqued his interest, but it quickly became an obsession. Hicks would repeatedly say, "Find another," every time they listened to a different station. He felt an inexplicable need to keep hearing the radio report over and over again."

At the time, Pankey was not considered a suspect, but Cash believed he needed to know all details about the investigation.

"In the early days of the case, he contacted law enforcement, but it wasn't until decades later that he became a suspect, as Cash explained."

Reports claimed that Pankey inserted himself into the case, raising eyebrows, but there was no evidence to prove his involvement in Matthews' disappearance.

The disappearance of children was a national concern during the Reagan administration, with Matthews' case receiving attention. The National Child Safety Council launched a project to print the picture of missing children on milk cartons across the country.

After Matthews disappeared, Pankey and his family relocated to different states before eventually settling in Idaho.

Hicks said their marriage continued to deteriorate over the years.

"Steve threatened my father, and I felt like I had to tread carefully to maintain peace. I was afraid of putting those I cared about in danger. You're in a coercive control situation, but it's like you're stuck. You feel powerless and unsure of how to escape. I was trapped, and when we left Greeley, I had no support system at all."

Despite relocating to multiple states, Pankey remained informed about the case, and in 1999, he told the Idaho Supreme Court that his conviction, which was later dismissed, was an attempt to force him to become an informant in Matthews' disappearance.

According to 9News, Hicks claimed that police were "harassing" him because he refused to "disclose information about Jonelle Matthews."

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Pankey allegedly asked his wife, "Do you truly believe I would harm her when she resembled you so closely?"

In 2008, when their son was murdered, Pankey mentioned Matthews during the memorial service.

In 2014, Pankey ran as a Constitution Party candidate for Idaho governor but was unsuccessful. He also ran unsuccessfully as a Republican gubernatorial primary candidate in 2018. In 2018, he was labeled a person of interest after claiming to have information about what happened to Matthews and requesting immunity from prosecution.

Then in 2019, Cash got a call he will never forget.

"He remembered the feeling of electric shock he experienced when he learned that some remains had been discovered. Although they had encountered remains before, this time it felt different. He felt a strong urge to visit the site and saw that the skull had braces on its teeth, just like Jonelle had when she disappeared. The colors of the clothing were still visible, and he felt a whirlwind of emotions and excitement. He was trembling and everyone was on high alert."

Matthews' death was ruled a homicide after her identity was confirmed with DNA technology.

Pankey's lawyers claimed that his actions may have appeared strange, but they maintained that the police lacked solid proof against him. Additionally, they highlighted that investigators had overlooked an alternative suspect who had passed away in 2007, according to the Tribune.

Still, law enforcement had no doubt they had Matthews' killer.

In 1984, Matthews disappeared and was later found dead. In 2022, Pankey was convicted of felony murder, second-degree kidnapping, and false reporting for his role in the disappearance and death of Matthews. As a result, he was sentenced to life in prison with the possibility of parole in 2040.

In 2021, jurors were unable to reach verdicts on the kidnapping and murder charges, and as a result, Pankey was put on trial again.

Hicks, who testified, said that she finally felt "safe."

"If he had not been found guilty, I would not have felt safe from then on out," she said. "So, I felt relief. But for the first time in 30-some years, I’m safe."

Cash has theories about the true motive behind Pankey's act, but it may never be known for certain.

Pankey saw Matthews as "nobody" to him, and Matthews was merely "collateral damage" due to his anger towards his church, which he "despised."

"Cash stated that the actions were carried out as a form of revenge against those who, in his opinion, had wronged him. He believes that the crime was callous and devoid of any empathy or humanity. He thinks that this makes it even more tragic because the monster, despite its actions, had so little emotion."

"Steve Pankey's neurosis drove him to feel the need to be fed information, which allowed him to play the game. To him, the case was all a game. If Steve Pankey had not inserted himself into the case, we would still be investigating the disappearance of Jonelle Matthews. Suspects in crimes often reveal themselves."

"Cases like this can be solved with the right connection and intentions, as Cash reflected, and it's never too late."

"The Girl on the Milk Carton" will air on Aug. 25 at 7 p.m. Planet Chronicle Digital and The Associated Press provided input for this report.