The Sunday evening child exchange began as usual in Jackson, Mississippi. On May 24, 1992, Richard Mosby and his new wife, Deborah, tried to drop off his two young sons, Bill and Joe, at their mother Gail’s home. They knocked, but she never came to the door.

“I was trying to figure out what’s going on, because my mom’s car is right there,” the now-adult Joe Mosby recalled in a preview clip for Snapped, airing Sunday at 6/5c on Oxygen. “I got the sense that Bill understood something was wrong.”

Before leaving with the boys, Richard and Deborah informed the man who lived next door about the curious situation. At 6 p.m. the neighbor used a spare key to enter Gail’s house.

Everything appeared to be in order, until he reached the main bathroom. “He was horrified to find that she was in her bathtub and Gail Mosby was dead,” said former prosecutor Cynthia Speetjens.

The neighbor called 911. Police and paramedics rushed to the scene, where they found Gail “unclothed … with her feet hanging outside the bathtub,” said former prosecutor Thomas R. Mayfield. “Her head was still underwater. She died from drowning. There was no other explanation.”

Clues tell conflicting stories at the scene

Police scanned the scene, which was tidy and orderly. The victim’s clothes were neatly folded. Officials recovered a journal and pills. The medications were “the kinds of things you would expect somebody who had been depressed to have been prescribed,” said Speetjens, adding that the evidence pointed in a particular direction.

“You put that package together,” she said, “and that kind of tips you over towards suicide.”

But before that determination could be made, police had to do a full evaluation of the scene. Charlie Smith, now retired from Jackson Police CSI, was concerned about several factors he observed. They included a bruise on Gail’s ankle and a small amount of blood in the bathwater.

But something else gnawed at him. “The thing that got me is the fact that the water was shallow,” he said in the Snapped preview. “Your body’s gonna fight. It’s not gonna let you drown in inches of water.”

So, Mayfield called in homicide investigators, and the shocking case was set in motion.

“They thought that my mom had committed suicide,” said Bill Mosby, looking back. “I never believed that for a second. I knew something happened to her.”

But what really occurred? Had something violent gone down in the final moments of devoted mom Gail Mosby’s life? Find out the answers in the new episode of Snapped airing Sunday at 6/5c on Oxygen.