A neighbor pleaded guilty Monday to kidnapping and killing a 5-year-old girl whose body was hidden in his cellar for days while hundreds of volunteers fanned across the city to search for her.

Craig Gregerson, 20, was immediately sentenced to life in prison without parole in a deal with prosecutors that spared him a possible death sentence.

Gregerson offered no explanation for his crimes but gave a handwritten letter to Destiny Norton's parents declaring, "I hate myself for what I did."

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"Her death was not the worst part. What I did after she was dead was unexcusable, sick and disgusting," Gregerson said, referring to a sexual assault on the body.

Destiny had been missing for eight days when police found her body stuffed in a plastic storage box in Gregerson's cellar, just two doors away, on July 24.

Authorities believe Destiny died within minutes of the abduction from her backyard July 16. Police said Gregerson lured the barefooted girl into his house, where he covered her mouth to muffle her screams, smothering her.

"You have every right to hate me, every right to want me dead and every right to never forgive me," Gregerson said in the letter to Destiny's family, which was released by 3rd District Court.

He said he took full responsibility for the girl's death.

"I hate that man for what he has done to my family," Destiny's mother, Rachael Norton, said in court without looking at Gregerson. "In the end I know God will judge him, and he will pay for what he has done."

Destiny's grandmother, Leslie D. Borchardt, was more blunt, referring five times to Gregerson as a "monster."

"I now know what hate is, and mine is unmatched," Borchardt said in a statement read to the judge by a family lawyer.

Outside court, Destiny's father, Rick Norton, was too overwhelmed to speak with reporters, saying he was leaving to take care of two other daughters, including Faith, who was born five weeks after the murder.

Prosecutor Robert Stott said the plea deal cut short years of trial and appeals and also spared the Norton family of more pain.

"They want it over," Stott said. "They want some peace. They want to be left alone. And they want to make sure Gregerson will never be able to harm anybody else."

Gregerson will live in isolation in a high-security cell except for shower time, and will have to be protected from other inmates who could seek retribution for the killing of a defenseless girl, Stott said.

He received a separate 15 year-to-life sentence on the kidnapping charge, even though it has no practical effect.

Gregerson's estranged wife was in court but said nothing after the hearing.

Gregerson had confessed to the murder after taking an FBI polygraph test during the search for Destiny. He used cleaning products to mask the odor of the dead body and had a white hazardous-materials suit hanging upstairs, according to court documents.

The Nortons' housemates kept a candlelight vigil in their yard during a search that had volunteers scouring city neighborhoods and nearby canyons.

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