Ariel Castro, who was sentenced to an 1,000 year prison term, was found hung in his prison cell on Tuesday night at the Correctional Reception Center in Orient, Ohio.
Castro, 53, was kept in his own cell for his protection and was checked by guards every 30 minutes, noted 19 Action News.
According to prison officials, Castro hanged himself between the 30 minute inspections.
Prison guards tried to resuscitate Castro, who was taken to the Ohio State University Medical Center. He was pronounced dead shortly before 11 p.m.
Castro kidnapped, tortured and raped Amanda Berry, Gina DeJesus and Michelle Knight in his Cleveland, Ohio house for about a decade.
Castro's son and three daughters were told of his suicide at about 1 a.m.
The Ohio State Patrol and the Ohio Department of Corrections will conduct an investigation of Castro's suicide.
Source: 19 Action News