Shaun Gayle Exclusive: Pregnant Girlfriend's Killing Exposes Obsessive Stalker

PHOTO: Shaun Gayle and Rhoni ReuterPlayCourtesy of Rhoni family
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After settling into the quaint suburb of Deerfield, Ill., outside of Chicago, Rhoni Reuter seemed to have everything.

The charming brunette loved her job at Macy's, and at 41, she learned she was about to have her first child -- a little girl – with her long-term boyfriend, former Chicago bear Shaun Gayle.

But all of that all changed on the morning of Oct. 4, 2007. Seven months pregnant, Reuter was getting ready to head for work but only got as far as the door.

Watch the full story on the latest episode of "20/20."

A 911 call from her neighbor painted a horrible picture: "I heard a women screaming and then a 'pop, pop' and then it went totally silent. I called my neighbor upstairs and she is pregnant and she didn't answer."

Deerfield police found Reuter dead on the kitchen floor of her apartment. She had been shot multiple times with a 9mm pistol, with two shots directed at her stomach, suggesting to authorities that the shooter was aiming for the unborn child. The shocking news quickly reached Reuter's hometown of Potosi, Wis., and her brother Thad Reuter.

"The minute I picked up the phone and heard my mom crying, I knew that something had happened," he said. "It's just something you never think is going to happen to your family. And I still think I'm going to wake up and it's going to be just a dream."

This was the first murder the town of Deerfield had seen in 30 years. Inside Reuter's apartment, officers found pictures of Shaun Gayle and immediately recognized him. Gayle was a member of the storied Chicago Bears team in 1985 -- the year they won the Super Bowl. Police learned he had been Reuter's boyfriend for 18 years.

The couple first met at a Bears charity event in Wisconsin. Gayle, who has never been interviewed since Reuter's death, agreed to speak exclusively to "20/20," and talked about the first time he met Reuter.

"She was in the crowd with some friends and we talked for a long time," he said. "We decided we wanted to keep in touch. It was a definite attraction and interest in one another."

Shaun Gayle Says He Was a Suspect at First

After retiring from the Bears, Gayle became a sports commentator, dabbled in real estate and even wrote several children's books. After Reuter became pregnant, Gayle said he was excited at the prospect of having a child of his own.

Although they dated for almost two decades, Gayle and Reuter never lived together. Gayle explained that the couple had an understanding that their relationship was not monogamous, which raised awkward questions for Reuter's family.

"I wouldn't think that my sister would have put up with that sort of relationship, knowing her as well as I do," Thad Reuter said. "Rhoni was strong-willed. Just don't believe that she would have put up with that sort of relationship."

Police quickly became curious about the nature of the couple's relationship, but before they could locate him, he called them, asking if Reuter was alive. When the officer told him to come to the station, Gayle began sobbing.

According to Deerfield Deputy Chief Rick Wilk, when Gayle arrived he was visibly shaken and upset. Wilk said he kept asking, "Who done this? How could this happen?"

But after observing how quickly Gayle composed himself, task force investigator Scott Frost was skeptical.

With no signs of robbery or forced entry, investigators immediately suspected Reuter may have known her killer. Gayle insisted that not only was he the "wrong man," but he believed the killer was his former girlfriend who he said had been stalking him.

Monika Kurowska was a striking Polish fitness model turned massage therapist, who Gayle had been romantically involved with for around seven months in 2006. It ended badly and with violence. After the breakup, Gayle said Kurowska would wait outside his apartment for him, and even shattered one of his windows in the middle of the night.

He told police he was also convinced Kurowska had been sending menacing letters to his friends and family. The anonymous letters were written in broken English and claimed Gayle was romancing 18 different women at the same time.

A Cyber-Stalker Revealed

When Rhoni Reuter received one of the letters, Gayle said she was devastated and he denied that the claims were true. She then stood by his side in court when he applied for a restraining order against Kurowska.

When Reuter's mother also received a similar nasty letter, she called Gayle, who assured her Rhoni was safe and that it was the work of a crazy fan. When Rhoni Reuter's body was discovered in her apartment, detectives recovered one of the letters inside her purse.

While being questioned by investigators, Kurowska denied sending the letters and said she was across town with a massage client the morning Rhoni Reuter's body was found, giving her an airtight alibi. Still not ruling out Gayle or Kurowska as suspects, police soon discovered that someone else had been watching Gayle's every move.

After scanning his computer, officers determined Gayle's emails had been tracked for years and the cyber-stalker was not Kurowska, but a new suspect: Marni Yang.

Yang was a divorced mother of three and Gayle's real estate agent. When police told him it was Yang, not Kurowska, who had been lurking behind his every key stroke, Gayle was stunned.

"They had a list of phone numbers and they tell me, 'Look at those numbers and see if you recognize the numbers,'" Gayle said. "So, I'm looking at them, and I realize, 'Oh, I know all of these numbers.' I said, 'This is what, is this my phone bill?' and they said, 'No. That's her phone bill.' Everyone that I would call, she called."

Suddenly all of the mishaps that had bedeviled Gayle for years made sense to him, such as flight and hotel reservations that were booked one day and mysteriously canceled the next.

Police then told him they believed Marni Yang was also hacking into Reuter's computer. Yang seemed to know where Reuter worked, where she lived – and that she was pregnant with Gayle's child.

As police further investigated Yang, her real estate broker image unraveled as a fraud. Gayle seemed to be her only client, and police told him Yang still bragged that she was his girlfriend.

But was Yang's self-delusional obsession with him powerful enough for murder? Having no physical evidence to tie her to Reuter's killing, police set up a dangerous uncover encounter. They asked Gayle if he would go to meet Yang while wearing a wire. Neither he nor the police have ever spoken about it publicly -- until now.

Watch the full story on the latest episode of "20/20."