GREENVILLE, S.C. -- Authorities said a 35-year-old prisoner serving a life sentence for murder killed himself with an overdose of prescription drugs.

Prisons spokesman Josh Gelinas told The Greenville News that investigators initially thought James Bell Junior died of natural causes when he was found dead in his cell in February.

Authorities said an autopsy found the overdose and the cause of death has been ruled a suicide.

Bell had been serving a life sentence since he was convicted of murder in Orangeburg County in 1993.

Gelinas said prison officials continue to investigate Bell's death.