St. Clair County Coroner Dennis Russell said Marquette Cummings, 24, died at 10:20 p.m.
He said Cummings’ body was transported to the Alabama Department of Forensic Sciences in Huntsville Wednesday to determine the exact cause of death.
Brian Corbett, Public Information officer for the Alabama Department of Corrections, said a fellow inmate admitted stabbing Cummings on Monday.
That inmate was identified as Timothy Gayle, 28, a convicted killer from Dallas County.
According to the Alabama Department of Corrections website, Gayle is not scheduled for release from the prison until 2035.
Corbett said Gayle, who was serving a 30-year sentence for murder, allegedly stabbed Cummings in self-defense.
Cummings was serving a life sentence with the possibility of parole after being convicted of murder in Jefferson County.
The Alabama Department of Correction’s Investigative and Intelligence Division continues its investigation into the death.
Corbett said the stabbing was unrelated to the ongoing protest by Alabama inmates over prison conditions.