A Southern California motorcycle club founder who killed three people in 1980 has been ordered to be released this week, following a terminal cancer diagnosis, prosecutors said Thursday.

Thomas Maniscalco, 77, has been incarcerated for nearly 40 years after his 1994 conviction on three counts of second-degree murder, with enhancements for being armed with a firearm, according to state prison officials. He was sentenced to life in prison and has been denied parole twice.

He was ordered released under California's compassionate release law, which was amended last year and allows for incarcerated people to be freed if they have a serious and advanced illness with an end-of-life trajectory.

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Maniscalco was the co-founder of the Hessian Motorcycle Club. Prosecutors said Maniscalco thought Richard Rizzone, another Hessian, was ripping him off in a counterfeiting and meth distribution ring.

Rizzone, his 19-year-old girlfriend Rena Miley and his bodyguard Thomas Monahan were killed in the 1980 Memorial Day attack in Rizzone's home in Westminster, which is about 25 miles southeast of downtown Los Angeles. All three were shot multiple times at close range.

Prosecutors said Miley, a police officer's daughter, and Monahan were slain so the killers could avoid witnesses.

Maniscalco and a fellow Hessian were convicted in the massacre. A third biker was killed by police in Oklahoma before charges could be brought.

Orange County District Attorney Todd Spitzer said Maniscalco, who will be released to his daughter who lives in the San Francisco Bay Area, poses a threat to public safety.

"He has taken no responsibility for the lives he destroyed and soon he will be a free man with nothing to lose," Spitzer said in a news release.

The state corrections department declined to comment Thursday. It was not immediately clear whether Maniscalco had an attorney who could speak on his behalf.