Frustrated by conditions in his cell, obsessed with the quality of prison food and convinced that guards were mistreating him, Cleveland kidnapper Ariel Castro committed suicide as the reality of living out his life in prison set in, two consultants concluded Tuesday.

The consultants, considered national experts on prison conditions, rejected suggestions that Castro may have died accidentally while seeking a sexual thrill, as an earlier review by the state prisons agency suggested.

The Sept. 3 death of the 53-year-old inmate was likely not the result of autoerotic asphyxiation, in which individuals choke themselves into unconsciousness to achieve sexual satisfaction, according to the consultants’ report.

The new report said all available evidence pointed to suicide, including a shrine-like arrangement of family pictures and a Bible in Castro’s cell, an increasing tone of frustration in his prison journal and coming to terms with spending the rest of his life in prison while subject to constant harassment.

Subsequent reviews by the Ohio State Highway Patrol and the Franklin County coroner reached the same conclusion, the report said.

“Based upon the fact that this inmate was going to remain in prison for the rest of his natural life under the probability of continued perceived harassment and threats to his safety, his death was not predictable on September 3, 2013, but his suicide was not surprising and perhaps inevitable,” the report said.

Fred Cohen, a retired professor at the State University of New York at Albany who helped monitor Ohio’s youth prison system as part of a federal court order, and Lindsay Hayes, who directs the National Center on Institutions and Alternatives and is an expert on prison suicides, conducted the review for the state.

Castro pleaded guilty in August to imprisoning three women in his Cleveland home for a decade while repeatedly raping and assaulting them. He fathered a girl with one of the victims.

He told a judge at sentencing that he suffered from addictions to sex and pornography. “I’m not a monster. I’m sick,” he said.

Castro was found dead kneeling in his cell with his pants down; he was hanging from a sheet attached to a window hinge, according to an earlier prisons report. He had just begun serving his sentence of life plus 1,000 years.

The two consultants said it was likely Castro was harassed by guards, based on interviews with inmates who said they had heard it.

“I don’t know if I can take this neglect anymore, and the way I’m being treated,” Castro wrote in a journal on Aug. 22, according to the report.

“I will not take this kind of treatment much longer if this place treats me this way,” Castro wrote on Aug. 31. “I can only imagine what things would be like at my parent institution. … I feel as though I’m being pushed over the edge, one day at a time.”

The report said Castro complained constantly about the quality of food and wrote in his journal he believed his food was being tampered with. He complained in late August that his cell and toilet were filthy.

Castro was housed at the state’s Correctional Reception Center south of Columbus, awaiting transfer to a permanent prison, when he died. None of the multiple health assessments he received indicated anything that would have required suicide-prevention measures, the consultants said.

Messages left Tuesday with Castro’s attorneys seeking comment about the report weren’t immediately returned.

The Ohio Department of Rehabilitation and Correction is committed to following recommendations in the report, spokeswoman JoEllen Smith said in a statement. They include beefing up staff training on suicide prevention and ending the use of online training.

Andrew Welsh-Huggins, Associated Press