(CNN) -- More than six years have passed since Steven Hayes broke into the Cheshire, Connecticut, home of the Petit family, setting off a deadly chain of events that ended in the death of a woman and her two daughters.
But even with time, Hayes struggles to explain exactly what happened and why.
"I started to lose it," he told the New Haven Register. "I looked out the window and saw an unmarked police car. And I just snapped."
Hayes and Joshua Komisarjevsky have been tried in the case, convicted and sentenced to death.
The two men entered the Petit home, beat and tied up William Petit and forced Jennifer Hawke-Petit to go to a bank and withdraw $15,000.
They then raped and strangled Hawke-Petit, 48, and molested 11-year-old Michaela before tying her and 17-year-old Hayley to their beds and setting the house afire.
The girls died from smoke inhalation. Their father managed to escape from the basement.
"I wasn't thinking right; I don't know what I was thinking. It was so unlike me. I'd never done anything like that," Hayes told the Register during an hour-long interview from prison.
He said it took him a year to even remember what happened in those final moments.
"I was told it was rage and stress or something. I just know that for a couple of minutes, I became somebody else," he said. "I'll never forgive myself for that."
William Petit, who remarried last year, did not respond to Hayes' comments.
But his sister-in-law, Cindy Hawke-Renn, said they were "too little, too late.
"How do you plan such behavior and allow people to die at your hands and burn alive, especially when you have children of your own? Snapped? Doesn't sound like an excuse to me," she told the Register.
Hayes said he was sorry for what he did and expressed feelings of "guilt, shame and remorse" about the deadly 2007 home invasion.
He reportedly tried to commit suicide before his trial started and told the Register that he wishes he had been successful.
"I don't deserve to live," Hayes told the newspaper. "I don't want to live."
However, he added, he no longer thinks about killing himself.
"I realize now I've got to live with this pain. It's something I'm supposed to live with," said Hayes.