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Monroe County District Attorney Michael Mancuso admits the “sensational” case of Pennsylvania Reverend Arthur “A.B.” Schirmer or “the sinister minister” continues to impact the small community.

The former pastor at Reeders United Methodist Church was sentenced in 2013 to life in prison without parole for the fatal bludgeoning of his second wife in 2008. The then-64-year-old was sentenced in Monroe County Court nearly two months after a jury convicted him of first-degree murder in the death of Betty Schirmer. That conviction brought an automatic life sentence.

The senseless killing is the subject of Oxygen’s docuseries “Accident, Suicide or Murder,” which retraces shocking true crime investigations, dissects red flags and points out strange behavior that puts tragedies in question. It features interviews with investigators and loved ones.

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The premiere episode focused on Schirmer, whose wife’s July 2008 death was seemingly caused by a car crash. However, state police began a more thorough investigation months later, when Joseph Musante committed suicide in Schirmer’s office after learning the pastor was in a relationship with his wife, the church secretary.

Mancuso, who helped put Schirmer behind bars for the rest of his life, participated in the show. He told Fox News that after viewing the crime scene photos of Betty’s crash, he knew it was far from an accident.

“Several things were apparent,” explained Mancuso. “Betty was bleeding before she was in the car, so before the accident. And the version of the accident given by Reverend Schirmer did not match the condition of the vehicle. There was hardly any damage to the vehicle. … And also, the reverend went out of his way to quickly cremate the body.

Monroe County District Attorney Michael Mancuso participated on Oxygen's “Accident, Suicide or Murder” series. — Oxygen

"So we found a great forensic pathologist, Dr. Wayne Ross… who showed us multiple directions of blows to the side of the head, four or five in number if I remember correctly, and believed it was with a cylindrical type object, something like a crowbar.”

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According to prosecutors, Schirmer clubbed Betty on the head with a crowbar, then loaded her into their car and staged a low-speed accident in an effort to conceal the crime. Schirmer took the stand in his own defense and testified that he was driving Betty to the emergency room for treatment of jaw pain when he swerved to avoid a deer and hit a guard rail.

Accident scene photo of Betty Schirmer's car crash. — Oxygen

Authorities concluded the fender-bender could not have caused Betty’s extensive head and brain injuries. Police also found her blood on the garage floor of their house, along with evidence that someone had tried to clean it up.

Accident scene photo from Betty Schirmer's car crash. (Oxygen)

“The reverend had no story for how the blood got in that garage and it just didn’t make any sense at all,” said Mancuso.

Reports claimed that weeks before Musante took his life, he learned that his wife Cindy was having an affair with the family’s trusted pastor. Mancuso clarified that Cindy was not involved in Betty’s slaying.

Accident scene photo from Betty Schirmer's car crash. (Oxygen)

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“There’s no evidence of that whatsoever,” he explained. “Cindy’s role in the whole thing was that she was romantically involved with the reverend and especially in a time period following the death. … We didn’t see any criminal reliability for Cindy. [But it was] real bad judgment that she had him move in her house shortly after the death of her husband, which was traumatic for the children.”

Arthur Schirmer mug shot.

Mancuso also described Shirmer as a “serial cheater.”

“He was also counseling people, including one female in particular, and we believe he was taking advantage of her because she was vulnerable,” he explained. “She wound up testifying at the trial. And he also had a very interesting relationship with a woman he had known for years. He was carrying on an affair with her once or twice a year. He would visit her at a hotel … That had been going on for years. She also wound up testifying.”

“He seemed to be much, much more on the prowl,” continued Mancuso. “I call him a wolf in sheep’s clothing. He was being called out on it over the years but always seemed to either find a way out of it or blame it on something else … Then he would get a fresh start somewhere else.”

The investigation into Betty’s death led police and prosecutors to take another close look at another mysterious death — that of Schirmer's first wife Jewel Schirmer. The fallen pastor had long claimed he was out for a run on April 23, 1999, when he returned home to find Jewel’s body in a pool of blood at the bottom of the basement steps. Prosecutors insisted Schirmer beat Jewel to death and attempted to make it look like an accident.

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At the time of Schirmer’s sentencing, his two daughters with Jewel said outside of court that they continued to believe in his innocence. Mancuso said Schirmer pled no contest to third-degree murder for Jewel’s death.

“I believe he received a 20-40 year sentence run concurrent to the life sentence,” he noted. “His appeals have all been denied. Currently, he filed a challenge to his representation here in Monroe County. We call it a Post Commission Relief Act petition. That was denied at the trial court level and is under appeal. They call that collateral review. And that’s not uncommon for cases like this.”

And there was no denying the sudden deaths of both women left residents feeling uneasy.

Betty Schirmer

“It was a very sensational case that came out of left field,” said Mancuso. “The people in the congregation, they were initially very split on the whole thing on what to believe had happened. Over time though, stats started to change as the facts came out. He found less and less support among the factions of the congregation that had originally been supportive of him. And it left a mark — there’s no doubt about it. That kind of thing is very telling on a tight-knit community. And that church was certainly tight-knit.”

Schirmer claimed on the stand that he and Betty had not been intimate for several years. He alleged Betty had been through menopause and wasn’t interested in sex. He also admitted he viewed pornography on his home computer. Still, he has maintained his innocence in both cases.

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Mancuso said he isn’t surprised Shirmer continues to claim he has had zero involvement in the deaths of his wives.

(Oxygen)

“Not at all,” he said. “I think he has every reason to claim innocence. His children with Jewel — he would never admit to them what he did to their mother. His continuing relationship with the former Mrs. Musante would be another reason for him not to admit to what he did. So, it’s not surprising. … I guess the term is narcissistic with a little bit of sociopathic kind of behavior. He’s all about himself, and he’ll never admit to the truth.”

Mancuso hopes the Oxygen special will shed new insight into the high-profile scandal — one that he could never forget.

“Never judge a book by its cover,” said Mancuso. “Appreciate law enforcement. There’s a very dedicated team that worked very hard for many years to make sure that justice was done, the truth came out and he would not be in a position to hurt anyone else.”

“The Sinister Minister” will air on Oxygen’s “Accident, Suicide or Murder” series on Friday, March 29 at 10:15 p.m. New episodes of "Accident, Suicide or Murder" air Saturdays at 7 p.m. on Oxygen. The Associated Press contributed to this report.