The neighbor charged with killing a 5-year-old girl planned the abduction and even wrote down his plans, court papers revealed Monday.

The papers show that Craig Roger Gregerson, 20, consented to an FBI polygraph test, then signed a full confession, telling authorities he had been keeping the girl's body in his cellar for eight days.

Gregerson lured Destiny Norton into his row house unit, where she "panicked and began to scream," said an affidavit police filed for a search warrant that was used to recover the girl's body. It said her body went limp after he smothered her with a hand.

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Then his phone rang. It was Gregerson's mother, who wanted him to pick up his 1-year-old daughter from his estranged wife's apartment.

Next, Gregerson carried the girl's body into his basement, where he sexually assaulted her, according to a probable cause statement police used to hold Gregerson in jail last week before he was formally charged.

Prosecutors on Thursday filed kidnapping and aggravated murder charges and could seek the death penalty if he is convicted.

Friends said Gregerson had volunteered to help search for the girl and lit a candle in a vigil outside the family's home while keeping the girl's body, which was found inside a plastic storage box.

A week after he hid her body, he used cleaning agents to mask the odor from his cellar, said the affidavit, which also revealed that Gregerson had a white Tyvek hazardous materials suit hanging from a curtain rod in full view of an FBI agent who paid him a visit.

The suit was seized as evidence along with letters Gregerson had written, untitled video tapes, a camera, cell phone, unidentified silver necklace and other household items.

The morning before her body was discovered on July 24, FBI Agent John Barrett met Gregerson at his residence, where he agreed to take a lie-detector test. The court papers did not say whether Gregerson passed or failed the test, but said his confession followed the exam.

Gregerson reportedly told FBI Agent Steve Fillerup, the polygraph examiner, that he had been planning Destiny's abduction "for some time" and that he "made written plans" for the crime. The affidavit didn't reveal those plans.

That opportunity came July 16 when Gregerson heard his dog barking in a backyard. He looked out a window and saw Destiny on the other side of a gate. Gregerson told authorities he stepped outside and opened the gate for Destiny, then lured her into his house.

It's still not clear how Gregerson did that, and friends of the Norton family insist Destiny was not a girl who could be easily lured by a stranger. Destiny's parents, Rick and Rachael Norton, have said they did not socialize with the neighbor and never would have given them permission to take the girl.

Police said they searched Gregerson's house early in the investigation but did not find the storage box that contained her body because it was hidden deep in the cellar. They return with a search warrant for a more thorough search after Gregerson offered a confession.

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