Two inmates killed a third inmate at a state prison in northeast California, officials said Tuesday.
Prison employees said they saw Jose R. Castillo and Victor M. Zapien attack Richard Prieto in an exercise yard at High Desert State Prison in Susanville Monday afternoon.
Correctional officers stopped the assault by firing a warning shot and chemical agents but Prieto was pronounced dead soon thereafter of puncture wounds to his chest, back, head and neck, state corrections officials said.
Two inmate-made metal weapons were found at the scene, officials said.
Prieto, 44, was serving a 22-year sentence from San Joaquin County for attempted second-degree murder.
Castillo, 26, was sentenced in Sonoma County to six years for assault with a deadly weapon on a first responder, and an additional six years for possessing deadly weapon by a prisoner, authorities said.
Zapien, 31, is serving a life sentence for a Stanislaus County murder.
The prison in Lassen County houses more than 3,100 inmates.