A Livermore man was killed in prison while serving life for murdering friend. Authorities say the victim has killed before, for the Aryan Brotherhood

DELANO — A Bay Area native who had allegedly killed the co-founder of a notorious Orange County skinhead gang has been killed in his prison cell, authorities announced Friday.

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.

Only Kober and Perez were in the cell at the time of the homicide, authorities said.

Kober, known in 2015 as a local methamphetamine and marijuana dealer around Livermore, was serving life for killing a longtime friend at the fourth hole of a golf course that year. But in 2018, he was implicated in a homicide once again, this time for a prison stabbing that had repercussions throughout the state’s prison system.

The victim was 48-year-old Devlin Stringfellow, an Orange County native and co-founder of the skinhead gang known as Public Enemy Number One, or PENI. Prosecutors now say his murder was ordered by an Aryan Brotherhood member named William Sylvester, who was convicted of racketeering charges last April and is awaiting a life sentence.

Stringfellow’s 2018 killing was a textbook Aryan Brotherhood hit, according to prosecutors. It occurred during exercise time at California State Prison, Sacramento. Someone struck Stringfellow in the head with a rock to stun him, then Kober and 49-year-old Stephen Dunckhurst allegedly moved in with knives, according to testimony at a trial for Sylvester and two other Aryan Brotherhood members.

While awaiting trial, Sylvester allegedly bragged about ordering Stringfellow’s death to other co-defendants. Another of PENI’s co-founders, Donald “Popeye” Mazza, later agreed to testify for the government in part due to his sadness over Stringfellow’s death, Mazza said during his testimony at the racketeering trial.

Kober was convicted and sentenced to life in 2015 for killing a friend, Kenneth Robert Ogden, 28, in Livermore amid growing tension between the two men. Kober had previously accused his girlfriend of having sex with Ogden and they had a dispute over money as well, authorities said at the time. Kober made money selling drugs and lived within a few yards of the Springtown Golf Course’s fourth hole, where Ogden’s body was found, according to court records.

Perez was serving a determinate term for assault with a firearm and gang activity, authorities said.