Officials say 43-year-old Gilbert Garcia and 33-year-old Rodolfo Cortez were seen attacking another inmate just before 6 pm Friday in the day-room at the Kern Valley State Prison.
Staff intervened, stopped the attack and began administering treatment to the victim.
37-year-old German Merino was taken to the prison's triage and treatment area, where he later died.
Investigators did recover an improvised weapon at the scene.
Both Garcia and Cortez are now in restricted housing as the investigation into the incident continues.