Jacob Kober, 35, was stabbed multiple times in his Kern Valley State Prison cell on Thursday, authorities said. His cellmate, identified as 39-year-old Matthew Perez, also sustained injuries consistent with a “prison manufactured weapon,” says a news release by the California Department of Corrections and Rehabilitation.

State corrections officials have launched a homicide investigation after a convicted killer from Alameda County died following an incident at a Central Valley prison Thursday evening.

An inmate at Kern Valley State Prison died Thursday after an apparent attack with an inmate-manufactured weapon, his cellmate also suffering injuries, prison officials said. Jacob Kober, 35, was pronounced dead at 7:52 p.