Washington - The former US bus driver jailed for life for kidnapping and raping three young women he held as sex slaves for a decade hanged himself in his cell late on Tuesday, while attempts to resuscitate him failed.
Ariel Castro was found hanging in his cell late on Tuesday, the Ohio Department of Corrections said in a statement carried widely by US news outlets.
Officials tried in vain to resuscitate the 53-year-old, according to the statement.
"He was housed in protective custody which means he was in a cell by himself and rounds are required every 30min at staggered intervals. Upon finding inmate Castro, prison medical staff began performing life-saving measures," the statement said.
Castro was pronounced dead at 22:52.
"A thorough review of this incident is underway," the statement by corrections department spokesperson JoEllen Smith said, according to KTLA.
Smith and other corrections department officials were not immediately reachable for comment.
Castro's crimes - keeping the three young women in what came to be known as a house of horrors and raping and otherwise brutalising them for around a decade - shocked the country and led to an outpouring of national pity for the three victims. They were abducted separately between 2002 and 2004.
Their names are Amanda Berry, now 27; Gina DeJesus, aged 23; and Michelle Knight, aged 32.
They ranged in age from 14 to 20 when Castro took them off the street in a working class neighbourhood of Cleveland, under the pretext he was offering them a ride in his car.
They escaped on 6 May when Berry managed to break open part of the front door and call out to a neighbour for help. Her frantic telephone call later to emergency rescue services was played and replayed over the media in the days after the three women escaped.
At the trial, as Castro sat in a bright orange prison jumpsuit, it emerged that they were brutalised, sometimes chained up and kept in abysmal conditions.
Berry had a daughter fathered by Castro.
The white delapidated house where they were tormented was demolished a few days after Castro was sentenced.
He got life plus 1 000 years.
At his sentencing hearing on 1 August, Castro had insisted he was not evil but rather addicted to sex.
"I'm not a monster. I'm sick," he pleaded.
Despite having pleaded guilty to 977 charges related to his victims' brutal decade-long ordeal, including many rapes and the murder of a foetus through beating its mother, Castro said he was not a violent man.
He pleaded guilty after prosecutors agreed not to seek the death penalty.
Castro said he had himself been sexually abused as a child and had grown up obsessed with sex, addicted to pornography and a compulsive masturbator.
He said he had not plotted the three kidnaps, but had acted on impulse.
"I am not a monster. I am a normal person. I am just sick. I have an addiction just like an alcoholic has an addiction," he said.
Michael Russo, the judge who sentenced Castro, described his crimes as unspeakable.
"Sir, there is no place in this city, there is no place in this country and indeed there is no place in this world for those who enslave others, those who sexually assault others and those who brutalise others," Russo said.
A tearful Michelle Knight, who was kidnapped at the age of 20, said in emotional testimony before the court that death would have been "so much easier" for her tormenter.
"I spent 11 years in hell, and now your hell is just beginning," Knight told Castro.