Sgt. Dennis Toomer says the hip-hop star, whose real name is Tauheed Epps, was walking with five members of his entourage near downtown on Sunday afternoon. They were approached by three men, one of them holding a handgun.
Toomer says one shot was fired as the rapper had his cellphone and wallet with credit cards and cash inside stolen.
Police say the suspected shooter apparently got away in a gray sedan.
The Atlanta-based rapper was in the Bay Area to perform at KMEL-FM's annual Summer Jam concert Sunday night at the Oracle Arena in Oakland.