EXCLUSIVE: Hot Car Monster Dad Who Let Toddler Bake to Death Was Allegedly HAVING AN AFFAIR With Neighbor — Who Cops Thought Was Silenced Because of Her Love With Twisted Sicko

The Arizona dad who killed himself the night before he was set to report to prison for the death of his toddler daughter was apparently having an affair with another woman behind his wife's trusting back, RadarOnline.com can reveal.

Christopher Scholtes agreed to a plea deal after he left his two-year-old daughter, Parker, trapped in his hot car to die while he drank beer, played video games, and searched for porn.

While Scholtes' wife, Erika, stood by her husband throughout his investigation and trial, the 38-year-old was allegedly involved in a secret romance with their married next-door neighbor.

Police reports indicate others on their block believed Scholtes was having an affair with 37-year-old Katelyn Schacht. Some of the neighbors who spoke with police seemed to blame the affair for Schacht's apparent reluctance to help with the investigation.

According to the report: "A common consensus in the neighborhood, although not confirmed, was that Katelyn and Christopher were having an affair, and that Katelyn would not come forward with what information she had due to this."

One neighbor described the two as having a "close relationship," while a third told cops Schacht frequently made excuses for Scholtes and their "special relationship", and would likely be uncooperative.

It's unclear if Erika knew of the affair speculations, but she had proven her loyalty to her husband in other ways in the past. Long before Scholtes "forgot" Parker was trapped in his boiling car, the unemployed dad had reportedly left the couple's other kids unsupervised and in danger as well.

The older children, now ages six and ten, told police their father "often left them alone in the car," something Erika had addressed with him in the past.

After Parker’s death, Erika texted him again in anger: "I told you to stop leaving them in the car. How many times have I told you?"

Records show she has also blasted Scholtes over allegations of drunk driving and abuse.

While Erika seemed to remain a fan of Scholtes, her mother made her objections to their union well known.

Shortly after Parker's death, a police interview with Cynthia King painted a disturbing picture of her son-in-law. King portrayed him as a self-obsessed "man-child" who was coddled and enabled by Erika.

After the tragedy, King stayed with her daughter and son-in-law, hoping to comfort them. Instead, King told investigators Scholtes seemed unfazed by the loss of his child.

"He was doing things that made me believe that he was just going about his business and that he wasn't grieving," King told police. "It wasn't even a week, and he asked (Erika) to have another baby."

Scholtes seemed more concerned for his PlayStation 5, which was confiscated by police as evidence. King revealed Scholtes rushed out to buy a replacement gaming system just two days after burying his daughter.

"Now, I understand that people grieve in different ways, but he was playing his PlayStation, and I had to leave, and that was the last time I was in that house," she said. "I was in disbelief that another PlayStation was purchased."

According to Parker's grandmother, the only time Scholtes did show emotion and cry was when he was forced to sell his beloved red convertible to help cover his legal fees.

Even at Parker's funeral, King said Scholtes found a way to make it all about himself.

"I had such rage in my body... even at the funeral, he was prancing around like it was a wedding," she slammed.