A Livermore man was killed in prison while serving a life sentence for the murder of a friend. Authorities say the victim had killed before, on behalf of the Aryan Brotherhood.

DELANO — A San Francisco Bay Area native who allegedly killed the co-founder of a notorious Orange County skinhead gang was killed in his jail cell, authorities said Friday.

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

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

Kober, known in 2015 as a local meth and marijuana dealer in the Livermore area, was serving a life sentence for killing a longtime friend on the fourth hole of a golf course that year. But in 2018, he was again implicated in a homicide, this time for a prison stabbing that sent ripples through the state’s prison system.

The victim was Devlin Stringfellow, 48, 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 last April and is facing a possible life sentence.

Prosecutors say Stringfellow’s 2018 killing was a classic example of the Aryan Brotherhood. It happened during a drill at California State Prison in Sacramento. Someone hit Stringfellow in the head with a rock to stun him, and then Kober and Stephen Dunckhurst, 49, allegedly came with knives, according to testimony at the trial of Sylvester and two other Aryan Brotherhood members.

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

Kober was convicted and sentenced to life in prison in 2015 for killing a friend, Kenneth Robert Ogden, 28, in Livermore, amid growing tensions between the two men. Kober had previously accused his girlfriend of having sex with Ogden and they also had a fight over money, authorities said at the time. Kober made money selling drugs and lived just yards from the fourth hole of the Springtown Golf Course, where Ogden’s body was found, court documents show.

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

Originally published: September 20, 2024 at 3:25 p.m.