SAN DIEGO (AP) — Authorities say an inmate has died six months after he was attacked at a Southern California prison.

State corrections officials said Friday that 37-year-old Roberto Belton was found unresponsive April 2 in a maximum security exercise yard at Richard J. Donovan Correctional Facility near San Diego.

He was taken to an outside hospital with serious injuries that officials say were consistent with having been severely beaten.

He died Thursday.

The corrections department and San Diego County Sheriff's Department are still investigating.

Belton was serving a life sentence from Alameda County with the possibility of parole for robbery and using a firearm as a repeat felon.

The prison houses about 3,800 inmates.