"This is just entirely against my nature," he told the agents. "... I'm not really religious, but what beliefs I do have would be pretty much best described as Buddhist."

He said he'd been planning his crime seriously for about a month, but he didn't have anyone in mind originally.

"I had kind of planned all along to probably get a kid, just mainly because they'd be easier to grab and easier to get rid of afterwards -- smaller and, you know, put up less of a fight," he said.

He said he stood outside his apartment door watching the children and trying to choose one.

"Well, I did kinda favor this girl a little," Underwood said of Bolin. "I had seen her and ... I was kind of like, 'Well, I really like her.' But then as I saw her more and more, I'd, you know, I'd think, 'No, I can't hurt her. You know, she's nice and I know her too well.'"

Underwood said Bolin had been to his apartment a few times because she liked his pet rat. April 12, 2006, Bolin came into his apartment to look at his pet.

"She was a very trusting kid that if it hadn't been me, it coulda ended up being someone else, 'cause, like I said, she just kinda wandered into my apartment," Underwood said. "I didn't, you know, force her in there or even ask her in."

He said she was in his apartment about 15 minutes while he tried to decide whether to go through with his plan.

Eventually, he picked up the wooden cutting board he'd kept on hand to subdue his victim and hit Bolin over the head to knock her out. Underwood said he had to hit her with the cutting board repeatedly while she pleaded with him to let her go, saying she was sorry.

"That's something that's, you know, haunted me forever since it happened," he said. "She started yelling, 'I'm sorry,' which you know, I'm like, 'What is she sorry for? She didn't do anything wrong. It's me. You know, I'm the one that should be sorry.'"

Underwood's crime didn't go as he'd anticipated. The body was much heavier than he thought it would be and he had trouble moving it. He dragged the body to his bedroom floor where he sexually assaulted the body but said he didn't actually have sex with it.

He said he decided to try and behead Bolin in the bathroom. The blood was all over the bathroom, he said.

"At this point, you know, I was just disgusted," Underwood said. "I was like, God, this mess. ... I guess I was already pretty upset, you know; I can't believe this, I wish I hadn't did it, you know, I wish I could take it back."

He couldn't undo it, though, so he stashed the body in a plastic tub until he could dispose of it, Underwood said.

"At the end I was like, 'No, I don't even wanna open the tub and look at this body. I'm just gonna drag the tub out to a field and set it on fire," Underwood said.