Ohio's prison system is reviewing how Cleveland kidnapper Ariel Castro - perhaps the most notorious figure behind bars in the state - managed to hang himself with a bedsheet while in protective custody.
Castro was a month into his life sentence for holding three women captive in his home for a decade when he took his own life on Tuesday night.
Protective custody involves checks every 30 minutes.
Ohio prisons director Gary Mohr ordered two reviews, less than a day after Castro was found in his cell and medical staff were unable to revive him. One review - normal in such cases - will look at the apparent suicide, while the other is an examination of Castro's circumstances and whether he received the proper medical and mental health care leading up to his death.
Christine Link, the ACLU of Ohio executive director, said in a statement: "As horrifying as Mr Castro's crimes may be, the state has a responsibility to ensure his safety from himself and others."
Castro, 53, had been taken off suicide watch while in county jail and was in protective custody in prison, a status reserved for high-profile inmates who could be in danger from other inmates.
As part of that status, he was in a cell by himself being checked every 30 minutes at an inmate intake prison south of Columbus, said JoEllen Smith, a rehabilitation and correction department spokeswoman. Prison medical staff performed CPR before Castro was taken to a hospital, where he was pronounced dead. State police are also investigating.
Residents in the westside Cleveland neighborhood where three women were secretly imprisoned reacted with scorn and grim satisfaction following news of Castro's death.
"He took the coward's way out," said Elsie Cintron, who lived up the street from the former school bus driver. "We're sad to hear that he's dead, but at the same time, we're happy he's gone, and now we know he can't ask for an appeal or try for one if he's acting like he's crazy."