Beneath the strings of red paper lanterns and narrow alleyways of the nation's oldest Chinatown lies an underworld, a place with a history of opium dens, gambling houses and gangland murders.

Federal investigators say it's also where Raymond "Shrimp Boy" Chow operated a criminal empire while projecting a public image of community servant.

The allegations against Chow are part of an FBI sting that names 25 other defendants, including state Sen. Leland Yee.

Investigators say Chow is the leader of a fraternal organization that doubles as one of the most powerful Asian gangs in North America. Chow's gang is said to have lured Yee through money and campaign contributions in exchange for providing official favors.

Yee announced Thursday he was stepping down from the race for California secretary of state.