Ariel Castro, who is serving lifetime imprisonment for holding three women captive and repeatedly raped them for almost a decade, was found dead in his prison cell Tuesday night, The Wall Street Journal reported Wednesday.

The 53-year-old Cleveland kidnapper was found hanging inside his cell at approximately 9:20 p.m. at the Correctional Reception Center in Orient, south of Columbus in Central Ohio. Prison officials speculate that Castro was the only person involved in his suicide.

Department of Rehabilitation and Correction Spokeswoman JoEllen Smith said Wednesday morning that Castro was discovered dead by the officers, who were tasked to check on him every 30 minutes at staggered intervals for he was under protective custody.

"Upon finding inmate Castro, prison medical staff began performing life saving measures," Smith said. "Shortly after he was transported to Ohio State University Medical Center where he was pronounced dead at 10:52 p.m."

Ariel Castro was a former school bus driver who was sentenced to life imprisonment in June after proven that he separately kidnapped three teenage girls between 2002 and 2003, and repeatedly raped them for nearly 10 years. The now-women were identified as Gina DeJesus, Michelle Knight, and Amanda Berry.

The Cleveland home where Castro held the women captive was demolished and forfeited as part of the agreement the prosecutors made in lieu of a death penalty.

"You took 11 years of my life away, and I have got it back," Michelle Knight said during the sentencing. "I spent 11 years in hell. Now your hell is just beginning."

Castro's attorney, Jaye Schlachet, told the Associated Press that he tried to have Castro undergo a psychological examination at the Cuayahoga Country Jail before turning him over to the state authorities.

Early last month, Schlachet and attorney Craig Weintraub said that Ariel Castro has a sociopathic disorder and added that they wanted researchers to examine him so that they could help stop other sociopaths at large.

The Wall Street Journal noted that Castro's death is the second high-profile suicide in an Ohio prison recently.

Billy Slagle was found hanged inside his cell on Aug. 4 just days before he was scheduled for execution. Slagle was condemned for fatally stabbing a neighbor.