SUSANVILLE, Calif. (AP) — An inmate at a Northern California state prison was stabbed to death Tuesday after he was attacked by two other prisoners, officials said.

Correctional officers spotted the attack on Richard Leyva, 37, in an exercise yard at California Correctional Center in Susanville, in the northeastern corner of the state.

Fellow inmates Luiz Ortega and Vincent Martinez attacked Leyva and ignored orders to stop until officers used pepper spray and two pepper-spray blast grenades, according to a statement from the California Department of Corrections and Rehabilitation.

Leyva had several stab wounds and died as he was being taken by ambulance to be airlifted to a hospital. Officers recovered two inmate-manufactured weapons.

Ortega and Martinez have been placed in segregation as the death is investigated, authorities said.

Leyva was serving a 14-year sentence from Monterey County for assault with a firearm. He had an additional eight-year sentence from Lassen County, where the prison is located, for assault by a prisoner with a deadly weapon.

Ortega 36, is serving a life sentence for a Stanislaus County murder.

Martinez, 37, is serving a sentence of more than 22 years from Kings County for attempted second-degree murder, possession of a controlled substance for sale, making criminal threats to cause great bodily injury or death. The conviction carried a street gang enhancement.