Three former Oklahoma State Penitentiary guards have been charged with second degree manslaughter and willful neglect of duty in the death if an inmate in August 2012.
David Willis, 29, David Anderson, 56, and Jay Nair, 46, were charged last week.
The inmate, Julius Parker, died of smoke inhalation after setting a fire in his prison cell on August 1st.
An affidavit filed in Pittsburg County court alleges that Willis, Anderson and Nair did not promptly check on Parker, despite seeing smoke coming from his cell.
Department of Corrections spokesman Jerry Massie says Willis was fired in September after an internal investigation into Parker's death.
Anderson and Nair have not yet been arrested. Parker was serving a 2005 sentence out of Tulsa County on a robbery with firearm conviction.
The Associated Press contributed to this story.