Wearing a mask and standing behind the front door of his suburban Chicago home, Drew Peterson spoke briefly about his missing wife, Stacy.
"I miss her," Peterson said.
Peterson has become the focus of the investigation, and police searched his home and his car Thursday. They have also sent divers and cadaver dogs to search a pond near the couple's home.
Stacy, 23, was on her way to visit her sister Sunday, but never showed up. Peterson, 53, said Stacy called him Sunday night and told him she was leaving. He said she has suffered from "mood issues" since a sister died.
He told reporters that he believes she left him for another man.
The couple's two young children are staying with neighbors.
Stacy Peterson's disappearance has also triggered renewed interest in the death of Kathleen Savio, Peterson's former wife, who drowned in a bathtub in 2004.
Neighbors of the Petersons say there were no outward signs of trouble between the two.
"I'd see them out holding hands walking around the block, playing with their kids," said neighbor Jim Lepper.
Family members and close friends tell a different story, though. One friend, Sherrie Mills, said Stacy described her marriage as abusive, and she fears the worst.
"She would not leave without her children," Mills said. "Her life was everything with those children."
Stacy's father, Anthony Cales, said he believes foul play is involved.
"I do. After four days, we've been looking for four days, and absolutely," Cales said.
Stacy and Drew had been married for four years. This was her first marriage, and his fourth.
In light of Stacy's disappearance, prosecutors are taking a second look at Savio's death three years ago in the bathtub of the couple's home.
Before she died, Savio had filed an order of protection against Drew, which said in part, "He wants me dead, and if he has to, he will burn the house down to shut me up."
The coroner ruled her death accidental.
Now Peterson said he wants the focus to be on his current missing wife -- not him.
"I'd like to be able to walk down the street and not get pointed at," he said.
The Associated Press contributed to this report.