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

April 14, 2011— -- 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."