A man killed in San Francisco's Outer Mission neighborhood earlier this week has been identified by the medical examiner as the president of the San Francisco branch of the Hells Angels motorcycle club, authorities said.

San Fransisco Police Department investigators say that Mark "Papa" Guardado, 46, was the person found shot at about 10:30 p.m. Tuesday outside a bar in the city's Mission District about a mile from the group's club house in the Dogpatch neighborhood. Guardado died a short time later at a local hospital.

Witnesses reportedly told authorities that Guardado fought with the man who shot him, then left on a motorcycle.

Residents and police are reportedly nervous now because there are reports that Guardado was killed by a member of rival motorcycle club The Mongols. Police are still investigating but haven't made any arrests in the case.

The Mongols are based in Southern California, but have local chapters in Modesto and San Jose. The two gangs clashed six years ago at Harrah's Casino in Laughlin, Nevada in violence that left three people dead.