Stacy Peterson's disappearance is grim lesson in coercive control, says pastor who counseled her

Stacy Peterson vanished from her Bolingbrook home nearly 20 years ago. The case remains unsolved. Her husband Drew Peterson has long been suspected of her murder. He has denied any involvement with her disappearance.

Neil Schori was a counseling pastor at a Bolingbrook church where Stacy, a young mother of two, first came to him to talk about her marriage. He shared with CBS News Chicago Investigators what she told him and why her tragic story isn't just about a notorious crime, but a masterclass in warning signs of domestic abuse that we are only now learning to recognize.

"Stacy told me about things in her life that were concerning," Schori said. "And she called it 'regular marriage issues.'"

Schori quickly learned her problems were actually deeply troubling. Drew Peterson, a veteran police sergeant, was 30 years older than his wife. They met when she was just a teenager.

"Drew would always accuse her of affairs," Schori recalled.

And he said Stacy would defend her husband.

"'It was because Drew loves me so much,'" he recalled her telling him. "'That's why he does that.'"

As an example, Schori said Stacy told him that if she took too long at the grocery store, Drew would call her multiple times.

"So I said, OK, well, tell me what you mean by a bunch," he said. "And she said, 'Oh, maybe 40 or 50.'"

Experts today would define that red flag not as simple jealousy, but coercive control.

"It's a pattern of behaviors that's designed to control and diminish another person," Schori explained.

Schori counseled Stacy alone and also had a few sessions with the two of them together. The last couple's session was ended abruptly by Drew in a way that left Schori on edge.

"This is a police officer with weapons. It was a very, very scary moment," he said. "And then she asked me to pray for her."

The coercive control kept escalating into something so terrifying, Stacy kept it secret for years. Until she told Schori.

"She just kind of shouted this out with no context: 'He did it.' I said, 'He did what?' She said, 'Drew killed Kathleen and made it look like an accident,'" Schori said.

Kathleen Savio, Drew's third ex-wife, was found dead in the bathtub of her Bolingbrook home in March 2004. Schori said Stacy was told she better give Drew an alibi, and that he had control over her when officers from his own police department showed up.

"They allowed him to sit next to her while they asked her where he was," he said. "It was horribly inappropriate. She said, 'Oh, he was right here the whole time.'"

Savio's death was ruled an accident. Stacy made Schori promise to keep her secret out of fear, and he had no way to prove what she told him.

"I felt conflicted, but I wanted to honor her as much as I could, too," he said.

Three years after Savio's death, and just two months after Stacy revealed her secret, she disappeared. It's now been 19 years. She's never been found and he's never been charged, but police call Drew the prime suspect.

Stacy's siter Cassandra Cales said she was also very much aware of the jealousu Schori described. She had a message to Drew Peterson back in 2011.

"She just couldn't put up with your jealousy and that's what we talked about the night before you murdered her," she said.

Pastor Schori told police about what Stacy had told him. That information, along with information shared by others who Stacy had confided in, prompted authorities to reexamine Savio's death. The accidental ruling changed to a homicide. Schori testified in that trial; his testimony proved crucial to helping convict Drew Peterson of first-degree murder.

Now, amid Domestic Violence Awareness Month, what Stacy said she lived through serves as a grim reminder of how dangerous jealousy and coercive control can be.

"I have huge regrets that I didn't know. I didn't understand coercive control," Schori said. "I didn't, as a pastor, know how to respond well to abuse. I know all those things now, but I know those things because of Stacy and because of Kathleen."

CBS News Chicago Investigators spoke to several members of Stacy's family who told us they were glad that this case could still shine a light on the red flags survivors should look out for all these years later. None of them wished to be interviewed at this time.

There's still an active investigation into Stacy's disappearance, for which Drew remains the prime suspect. Anyone with information is encouraged to contact the FBI at their national tip line, 1-800-CALL-FBI (1-800-225-5324) or the FBI Chicago Field Office at 312-421-6700. Illinois State Police also maintain a Stacy Peterson tip line at 815-740-0678.

Drew Peterson is currently serving a 78-year sentence for Kathlee Savio's murder.