Four California inmates were killed at three state prisons, including two at a facility north of Bakersfield a day apart, corrections department officials said Monday.

“They’re all unrelated,” said department spokeswoman Terry Thornton.

Officials say two inmates fatally stabbed Michael M. Ramadanovic, 65, on Friday at High Desert State Prison in Susanville.

The attackers didn’t stop until correctional officers used chemical agents and fired a warning shot.

Ramadanovic was serving a life sentence for a Merced County murder, with another six-year sentence for assault with a deadly weapon in prison.

The suspects are Rodney Rice and Robert Smith, both 28.

Rice was sentenced last year on a second-strike conviction involving injuring someone within seven years of a previous conviction. He has served time for various crimes, ranging from auto theft to assault with a deadly weapon.

Smith is serving time for various crimes, including a prison assault, and in March was sentenced in Tuolumne County for assault with force likely to produce great bodily injury.

Ramadanovic Convicted of First-Degree Murder in 1981

Jerry D. Bigelow and Ramadanovic escaped from a Canadian jail and hitchhiked to California in 1980. At trial, authorities said the two men robbed and kidnaped John Cherry, a Chico carpenter who had given them a ride. They then shot Cherry to death in a Merced County cornfield.

Ramadanovic pleaded guilty in a trial separate of Bigelow and was sentenced to life without the possibility of parole.

Bigelow was released from San Quentin’s death row in 1989 after he was acquitted in a retrial.

Two Inmates Killed at Delano Prison

Robert Beltran, 50, was fatally stabbed by three other inmates as he left his cell at Kern Valley State Prison in Delano on Friday, officials said.

That’s in a different part of the same prison where a day earlier two inmates fatally stabbed convicted murderer Robert Hargrave, 48.

Beltran was serving a life term for attempted second-degree murder and kidnapping. Officials did not immediately say if they had reason to think the two slayings are related.

The three being held on suspicion of killing Beltran are Charles Garibay, Rafael Navarro, and Guillermo Navarro. The victim and suspected attackers are from Los Angeles County.

Guillermo Navarro, 38, is serving a life term for murder. He is not related to Rafael Navarro.

Rafael Navarro, 32, is serving a 25-year sentence for armed robbery with gang enhancements. He has additional sentences for drug possession and attacking another inmate while in prison.

Garibay, 34, is serving a 46-year sentence for assault with a semi-automatic firearm on a peace officer, attempted carjacking and attempted murder, and another four years for possessing a weapon in prison.

Inmate, 75, Killed in Vacaville

Also on Thursday, officials at the California Medical Facility in Vacaville said they found 75-year-old Tuc X. Tran unresponsive in his cell with multiple injuries to his head and face. His next of kin were notified on Monday. He had been serving a life sentence for a Riverside County murder.

They are holding his cellmate, James A. Norton, 39, as a suspect. He is serving a two-year sentence from Mendocino County for causing a fire on forest land.