On Nov. 16, 2012, the Prescott police department in Arizona received a call from Angel, a 19-year-old caregiver who said his patient, David Mueller, passed in his sleep. But even though all signs pointed to a natural death, David’s wife Cynthia Mueller quickly becomes a person of interested. Now, in the 400th episode of Oxygen’s Snapped, homicide investigators reveal how they unraveled the truth.

David, who was 52 years old at the time of his death, has been bed-ridden and suffered from amyotrophic lateral sclerosis (ALS) which is also commonly known as Lou Gehrig’s disease. Prescott Police detective James Lamerson explained that even though it seemed like David passed in his sleep, police still responded to Angel’s call, “just to make sure that nothing suspicious took place.”

At the scene, police found David’s 48-year-old wife, Cynthia, at his bedside and she seemed visibly upset. “When the authorities showed up, Cynthia was still on the floor bawling,” Angel said in his confessional. But she was being comforted by another caregiver, 61-year-old Charles “Chuck” Todd.

Investigators said there was no sign of a struggle or trauma, but they eventually learned that there was something more sinister at play. According to the Associated Press, Cynthia and Chuck were eventually arrested and charged with killing David by suffocation. Deputy County Attorney Steve Young said Chuck eventually confessed, telling authorities that he was having an affair with Cynthia and that they killed David together.

Cynthia had allegedly told Chuck that David was “dying,” and she asked Chuck how they could “make it quicker,” Steve explained. Chuck then suggested that they suffocate David with a plastic trash bag and a pillow, and Chuck assumed that he and Cynthia would continue to have a relationship once David died — but that didn’t go the way he’d hoped. “She decided she doesn’t need him anymore,” Steve said.

Cynthia denied the allegations, but she was still convicted of murder in 2015 and she is currently serving a life sentence, according to local paper The Daily Courier.

The 400th episode of Oxygen’s Snapped will air on Sunday, Nov. 11th at 6 p.m.ET/PT.

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