SACRAMENTO, Calif. >> A prisoner slain by fellow white inmates at a California prison was a founder of Public Enemy Number 1, a white supremacist prison and street gang, law enforcement and watchdog groups confirmed today.

Devlin “Gazoo” Stringfellow, 48, helped start the group known as PENI, which grew from the Southern California punk music scene in the 1980s into what the Anti-Defamation League calls a hybrid, racist, skinhead gang.

Stringfellow was stabbed repeatedly in an exercise yard Wednesday by two other prisoners armed with inmate-made weapons, said Lt. L.A. Quinn, a spokesman at California State Prison, Sacramento.

He identified them as Jacob Kober, 29, and Stephen Dunckhurst, 49. No charges have been filed, and experts could not immediately say if they are gang members.

Quinn said officials didn’t have a motive.

All members of PENI were previously made members of the Aryan Brotherhood prison gang, said Matthew Buechner, a former gang investigator with the California corrections department.

Stringfellow was the second high-profile gang leader slain at the maximum security prison east of Sacramento in recent years.

Hugo “Yogi” Pinell, 71, a purported member of the Black Guerrilla Family, was slain in 2015 after he was freed from decades in isolation following a bloody escape attempt at San Quentin State Prison in 1971. Pinell denied gang involvement.

Buechner said Stringfellow had been a target of fellow gang members for years.

“He was a loud mouth and (the Aryan Brotherhood) does not want attention,” Buechner said in an email. Its members lure targets into thinking they are safe, “then strike as violently as possible to send a message to enemies and membership to stay in line.”

Stringfellow had been in and out of prison repeatedly since 1991, mostly on drug and weapons charges with added time for engaging in gang activity. He was set to be released in 2020 after completing a six-year sentence on drug, weapons and assault charges.

His attorney in that case, Nima Farhadi of the Los Angeles County Public Defender’s Office, did not return telephone messages Friday.

Kober is serving a life sentence for a 2012 Alameda County murder. Dunckhurst was initially serving a three-year term for a Shasta County robbery but now has a life sentence for vehicle theft and a weapons conviction.

Internal gang slayings are not uncommon, said Joanna Mendelson, a senior investigative researcher with the Anti-Defamation League’s Center on Extremism who was among those identifying Stringfellow as a PENI founder.

“The movement is characterized by paranoia, infighting and violence both directed against enemies as well as even their own members,” she said in an email. “Putting a hit on their own ‘brothers’ is not uncommon.”