Last Updated Sep 4, 2013 8:22 AM EDT
Updated 10:47 a.m. EST
(CBS) CLEVELAND - Ariel Castro, the Cleveland man who kidnapped three women and sexually abused them while holding them captive in his home for the better part of a decade, was found dead in his prison cell late Tuesday evening.
The 53-year-old was believed to have committed suicide, officials said, having been found hanging in his cell. Prison medical staff performed CPR before he was transported to an area hospital, where he was pronounced dead.
So far, officials have not specified how the inmate, who had been under protective custody because of his notoriety, could have killed himself, reports CBS affiliate WOIO in Cleveland. Protective custody warrants checks on an inmate every 30 minutes.
Castro had been sentenced on August 1 to life in prison, plus 1,000 years, for kidnapping and sexually assaulting Amanda Berry, Michelle Knight and Gina DeJesus while holding them captive in his house. He had entered a guilty plea to avoid trial.
An attorney for the three women told CNN they will not be making a statement about Castro's suicide.
The mindstate of the kidnapper prior to his alleged suicide is also not clear. Medical and psychological tests are typically conducted for someone who was in Castro's position, although officials haven't commented on their results yet.
When Castro was being held in Cuyahoga County Jail following his arrest in May, his activity had been logged every ten minutes. However, he was taken off the jail suicide watch in early June after authorities determined he was not a suicide risk.
Castro's attorneys tried unsuccessfully to have a psychological examination of Castro done at the Cuyahoga County Jail, where Castro was housed before he was turned over to state authorities following his conviction, his attorney, Jaye Schlachet, told The Associated Press early Wednesday. Schlachet said he could not immediately comment further.
In an interview last month after Castro's conviction, Schlachet and attorney Craig Weintraub said their client clearly fit the profile of sociopathic disorder and that they hoped researchers would study him for clues that could be used to stop other predators.
When investigators searched Castro's home following his arrest, they found a handwritten note he had apparently written in 2004 that not only confessed his crime, but also indicated he was contemplating suicide.
According to a law enforcement source, Castro wrote about his whole life in the note. It stated that he was abused by his parents as a child and that he was raped by an uncle. It detailed the abduction of each of the three women, and Castro even called himself a "sexual predator," CBS News correspondent Dead Reynolds reported at the time.
In addition to being confessional, the 2004 note was also delusional, blaming each of the women for their own abduction. However, it asked that whatever money he has be donated to his victims in the event of his death.
Castro's victims disappeared separately between 2002 and 2004. They were rescued from Castro's Cleveland home on May 6 when one of the victims, Amanda Berry, broke the front door and yelled for help.
"Help me," she said in a 911 call on a neighbor's phone. "I've been kidnapped, and I've been missing for 10 years and I'm, I'm here, I'm free now."
The two other women were so scared of Castro that they held back initially even as police officers began to swarm the house. But quickly they realized they were free.
"You saved us! You saved us!" another of the captives, Michelle Knight, told an officer as she leaped into his arms.
Castro was arrested that evening.
It was later revealed that he had fathered a child with Berry.
At an August 1 hearing Castro gave an emotional defense to the court for his behavior.
"People are trying to paint me as a monster, and I'm not a monster," Castro said. "I'm sick."