Kevin Underwood, a 26-year-old grocery store stocker in a small community 40 miles south of Oklahoma City, is expected to appear in court for the first time since his arrest Friday.
Investigators searched his apartment after he aroused their suspicions at a checkpoint, and found a large plastic tub in a bedroom closet. According to a police affidavit, he confessed that he killed Jamie Rose Bolin, telling FBI agents: "Go ahead and arrest me. She is in there. I chopped her up."
Underwood also joked about cannibalism on his online diary, discussed the effects of not taking his anti-depression medication and mentioned "dangerously weird" fantasies.
All he wanted in life, Kevin Ray Underwood wrote in his blog, was "to be able to live like a normal person."
People who knew Underwood described him Sunday as a quiet, "boring" and seemingly trustworthy young man. His mother who lived across town called him a "wonderful boy."
"This is something that I don't know where it came from," Connie Underwood said of her son through tears in a brief telephone interview with The Associated Press. "I would like to be able to tell her family how sorry we are. I just feel so terrible."
Jamie's unclothed body was inside a tub in Underwood's apartment, along with a towel used to soak up blood, officials said. Police said that, while there were deep saw marks on the girl's neck, she had not been dismembered.
Underwood lived alone in an apartment downstairs from the one where Jamie lived with her father. Tim Bayer, the apartment complex's manager, is baffled since nothing in Underwood hinted at the face of evil, CBS News correspondent Mark Strassmann reports. "He was a quiet person," Bayer said.
Authorities believe Kevin Underwood killed the girl Wednesday, when she disappeared after going to a library, by beating and smothering her.
Investigators found meat tenderizer and barbecue skewers that he planned to use on the body, McClain County District Attorney Tim Kuykendall said.
On his blog, an online diary that he had kept since September 2002, Kevin Underwood described himself as "single, bored, and lonely, but other than that, pretty happy." His website also lists many of his personal hates, everything from the continuing focus on 9/11, all the way down to certain cartoon characters, Strassmann reports.
He mentions cannibalism, asking "If you were a cannibal, what would you wear to dinner?" and responding: "The skin of last night's main course."
In an entry dated Feb. 4, 2006, Kevin Underwood wrote that he struggled with depression and social interaction.
"Pretty much the only time I believe in God is when I blame him for something," he said. "Or, when I'm really depressed, to cry and beg him to make me better, to make whatever is wrong in my brain go away, so that I can live like a normal person."
"That's all I want in life, is to be able to live like a normal person."
He wrote that he rarely left his apartment for long stretches, except to go to work and to buy food. "I just sit here at the computer every minute of the day, when I'm not at work. A week or so ago, I spent my day off sitting here at the computer, barely moving from the chair, for 14 hours."
He said one of his main interests was the online role-playing game "Kingdom of Loathing," in which stick figures battle one another.
In September 2004, he wrote that his depression deepened after several months without taking the medication Lexapro, an antidepressant also used in the treatment of anxiety disorders.
"For example, my fantasies are just getting weirder and weirder. Dangerously weird," he wrote. "If people knew the kinds of things I think about anymore, I'd probably be locked away. No probably about it, I know I would be."
Kevin Underwood worked for nearly seven years at a Carl's Jr. restaurant, where shift leader Bill Verdan described him as a quiet person who kept to himself. "He did a good job," Verdan said Sunday.
However, he said Kevin Underwood, who quit about a year ago, was a "boring" man who rarely smiled.
"Just his tone of voice, he just sounded dull," Verdan said. "Trying to get a smile out of him took an act of Congress."
Verdan said he and his wife and young daughters never suspected anything unusual.
Meanwhile, Bolin's family is now left to deal with their anguish. "I want to get it to a point where we can handle it without collapsing," a family member told CBS News.