"I heard screaming upstairs and her friend Mary went upstairs and she was dead in the bathtub," Peterson said. "I checked for life signs and I knew at that particular time I didn't belong there, so I called for additional police units to show up and take charge of the scene."
His first concern, he said, was for their children.
"I got them out of there as quickly as possible after it happened. They went back for their things and it was kind of emotional but it was kind of like, what can you do? Life goes on."
An autopsy found that Savio had fallen into the bath and drowned. By that point, Stacy Peterson had already given birth to a child and, a year later, in 2005, she had a second. But in 2006, she lost her half-sister to colon cancer and was devastated.
"She took it very bad," Peterson said. "We had her [see] a psychologist and on medication. ... And the relationships towards me and the kids and everything started breaking down at that time."
In October 2007, he says, his wife seemed to take matters into her own hands.
"She said she was leaving," Peterson said. "She found somebody else. She'll be gone for a while. And I can't remember. It's been played over again and again in my head her exact words. ... Basically, the gist of it was that she found someone else. She was leaving. She'd be gone for a while.
"I remember the snottiness in her voice," he continued. "I was like, 'What am I supposed to do?' And she said, 'deal with it.' And that was pretty much the conversation."
As for whether he was surprised that a mother would consider abandoning her children, he said, "Stuff happens. Mothers kill their kids. Mothers kill their spouses. Mothers do strange things.
"They become emotionally distraught and it becomes too much for them. They are overloaded. Millions of things. I've talked to many psychiatrists-psychologists about this. It happens. Is it unlikely? Yeah. It's very unlikely, but it happens."
The police launched a missing persons inquiry. They never located Stacy Peterson but they did find some intriguing correspondence.
She had sent an e-mail to friends prior to her disappearance, saying, "As I mature with age, I'm finding that the relationship I'm in is controlling, manipulative and somewhat abusive."
"That doesn't even sound like something she would say," said Peterson, "so I really question the origin of that e-mail."
The minister at the local church also emerged, claiming he knew a different story about how Peterson's third wife Kathleen had come to die in the bath. Neil Shory says Stacy Peterson told him her husband confessed to killing his third wife.
"Right. I heard that, but again, wouldn't you seek out authorities if you heard that coming out of somebody's mouth?" Peterson asked. "And I really question whether she really said it or it's something he fabricated."
Peterson claims the minister's story has changed since he initially came forward. But if it is true, why would Stacy go and say such a thing about him?
"Maybe she was planning to divorce me," Peterson said. "Was she doing this to get rid of me? What better way to get rid of me than to say I did something that I didn't do. Have me locked up. You know, she gets the whole ball waxed then. She don't even have to bother going through a divorce. She gets everything and I'm in prison."