OKLAHOMA CITY -- Oklahoma is preparing to execute a man who killed a 10-year-old girl in what would be the nation's 25th and final execution of the year.

Kevin Ray Underwood is scheduled to die by lethal injection on Thursday, his 45th birthday, at the Oklahoma State Penitentiary in McAlester. Underwood, a former grocery store worker, was sentenced to die for killing Jamie Rose Bolin in 2006 as part of a cannibalistic fantasy.

Underwood admitted to luring Jamie into his apartment and beating her over the head with a cutting board before suffocating and sexually assaulting her. He told investigators that he nearly beheaded the girl in his bathtub before abandoning his plans to eat her.

Oklahoma uses a three-drug lethal injection process that begins with the sedative midazolam followed by a second drug that paralyzes the inmate to halt their breathing and a third that stops their heart.

During a hearing last week before the state's Pardon and Parole Board, Underwood told the girl's family he was sorry.

"I would like to apologize to the victim's family, to my own family and to everyone in that room today that had to hear the horrible details of what I did," Underwood said to the board via a video feed from the Oklahoma State Penitentiary.

The three board members in attendance at last week's meeting all voted against recommending clemency.

Underwood's attorneys had argued that he deserved to be spared from death because of his long history of abuse and serious mental health issues that included autism, obsessive-compulsive disorder, bipolar and panic disorders, post-traumatic stress disorder, schizotypal personality disorder, and various deviant sexual paraphilias.

"Whatever deviance of the mind led Underwood to abduct, beat, suffocate, sexually abuse and nearly decapitate Jamie cannot be laid at the feet of depression, anxiety or (autism)," prosecutors wrote in their opposition to Underwood's clemency request. "Underwood is dangerous because he is smart, organized and driven by deviant sexual desires rooted in the harm and abuse of others."

In a last-minute request seeking a stay of execution from the U.S. Supreme Court, Underwood's attorneys argued that he deserves a hearing before the full five-member parole board and that the panel violated state law and Underwood's rights by rescheduling its hearing at the last minute after two members of the board resigned.