Ariel Castro is shown in a Cuyahoga County Jail booking photo.
Kidnapper and rapist Ariel Castro was found hanged in his jail cell just a month after being sentenced to life in prison plus 1,000 years for holding three women captive in his Cleveland home, a prison official said early Wednesday.
A county coroner confirmed Wednesday that the cause of death was suicide by hanging.
Medical officials tried to revive the 53-year-old former school bus driver after he was discovered around 9:20 p.m. CT Tuesday at the Correctional Reception Center in Orient, Ohio, authorities said.
Castro was transported to Ohio State University Medical Center in nearby Columbus but was pronounced dead at 10.52 p.m.
Authorities said a "thorough review of this incident is under way." Franklin County Coroner Jan Gorniak said the cause of death was suicide by hanging, and said his injuries were consistent with using a bedsheet.
He does not appear to have left a note.
Castro had been housed in protective custody, which means he was in a cell by himself. Guards were making rounds every 30 minutes at staggered intervals, according to the Ohio Bureau of Prisons.
Speaking to NBC's TODAY on Wednesday, Castro's attorney Craig Weintraub said that his client's family was devastated by the news.
He said Castro had been moved to the prison about two weeks ago and that relatives had visited a couple of times since then.
Weintraub acknowledged that the reaction of many people would likely be "good riddance," but said that he planned to get to the bottom of the circumstances surrounding Castro's death.
"This is a human being," he added. "We are not going to let this go."
The three women Castro kidnapped had disappeared separately between 2002 and 2004, when they were 14, 16 and 20 years old.
His victims - Amanda Berry, Gina DeJesus and Michelle Knight - escaped May 6 after Berry broke through a storm door while Castro was out of the house.
"Help me," the 27-year-old Berry said in a 911 call. "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 later that day a short distance from the home.
On Wednesday, an attorney for Knight said she and the other survivors would not be releasing a statement about Castro's death.
Castro was sentenced Aug. 1 to life in prison plus 1,000 years on his guilty plea to 937 counts including kidnapping, rape and a charge of aggravated murder under a fetal homicide law for a forced miscarriage.
At the sentencing, Knight confronted Castro, reading a damning statement.
"I spent 11 years in hell," the 32-year-old Knight told her tormentor. "Your hell is just beginning."
In July, Knight thanked police and well-wishers in a handwritten note. "I am overwhelmed by the amount of thoughts, love & prayers expressed by complete strangers," she wrote. "Life is tough, but I'm tougher."
In a memo filed ahead of Castro's sentencing hearing, Cuyahoga County Prosecutor Timothy McGinty described him as "remorseless" and said he "serially abused them physically, emotionally, and sexually on a daily basis."
According to McGinty's document, Castro lured Knight into his car in 2002 by promising her he would give her a puppy for her son. It also revealed the women were restrained with chains, fed one meal a day and allowed one or two cold showers a week.
McGinty had harsh words on Wednesday after Castro's death: "These degenerate molesters are cowards. They con and capture vulnerable children. This man couldn't take, even for a month, a small portion of what he had dished out for more than a decade," he said in a statement.
"Let this be a message to other child kidnappers: There will be a heavy price to pay when you are caught. You won't enjoy the captive side of the bars."
In his own statements at the sentencing, Castro put much of the blame on his victims. "I am not a violent person. I simply kept them there without being able to leave," he said. "These people are trying to paint me as a monster. I'm not a monster, I'm sick."
Of the daughter he fathered with Berry who was born in captivity, Castro told the court: "She'll probably say, 'My daddy is the best daddy in the world.' Because that's how I tried to raise her in those six years. So she wouldn't be traumatized or anything like that."
Castro's attorneys had 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 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, the AP reported.
McGinty, the prosecutor, had acknowledged after Castro's sentencing that a suicide note and confession written by Castro was found by authorities at his residence when they searched his home following his arrest in May.
The home at 2207 Seymour Avenue in Cleveland where Castro held the three women has since been demolished. On Wednesday, Castro's former neighbors along Seymour Avenue expressed shock as they woke up to the news of his death.
"It's bad. Ariel was a good neighbor all the time," said Aurora Marti, 76.
"I think it's sad he did that," said Emma Jean Mondi, 55. "He didn't want to sit in jail for the rest of his life."
Added John Crawford, 52, "I think that maybe he didn't have much left for him. Maybe there were problems at the prison, like with inmates."
Carina Hughes, 34, who lives a couple blocks away, decided to come visit the spot where the women had been held after hearing Castro was dead.
"I just needed to be here. I just relate to the girls," she said. "It could have been me. It could have been my daughter."
She said she saw today as a day for celebrating.
"The girls never have to worry about him getting out," she said. "He's just gone."
Appearing on TODAY, Weintraub described his client as "deeply disturbed" and said there was "no doubt he had psychological problems."
Castro's is the second high-profile suicide at an Ohio prison within the span of a month. On Aug. 4, death row inmate Billy Slagle was found hanged in his cell just days before his scheduled execution. He was condemned to death for fatally stabbing a neighbor in Cleveland.
By Mark Stevenson, Hasani Gittens, and Matthew DeLuca, NBC News