News Releases

Kern Valley State Prison Officials Investigate the Homicide of an Inmate


Contact-Lt. John Melvin, (661) 721-6314

DELANO – Officials at Kern Valley State Prison (KVSP) are investigating an incident which occurred yesterday on the Facility B recreational yard as a homicide.

On Thursday, April 30, at approximately 1:30 p.m., correctional officers responded when inmates Matthew Thornton and Michael Arzaga began attacking inmate Robert Hargrave with an inmate-manufactured weapon. The officers ordered them to stop and when the attackers did not comply, they used chemical agents to stop their assault.

Hargrave suffered multiple stab wounds to his back, chest and abdomen. He was taken to the institution’s Triage and Treatment Area and was later taken to an outside hospital for treatment. He was pronounced deceased at 2:40 p.m. at the hospital by the on-duty physician.

Hargrave, 48, had been in prison since May 1994. He was admitted from Riverside County and was serving life without the possibility of parole for first-degree murder.

Inmate Thornton, 38, was admitted from San Diego County on May 11, 2009, to serve a 14-year sentence for attempted second-degree murder and a five-year enhancement for prior felony conviction of a serious offense.

Inmate Arzaga, 47, was received on March 23, 1998, from San Diego County to serve a life sentence with the possibility of parole for second-degree murder.

The KVSP Investigative Services Unit and the Kern County Sheriff’s Office are investigating. The Office of the Inspector General has been notified.

KVSP opened in 2005 and houses 3,538 minimum-, medium-, maximum- and high-security custody inmates. KVSP offers academic classes and vocational programs and employs approximately 1,800 people. For more information, visit

inmate Matthew Thornton
inmate Michael Arzaga