LOS ANGELES (AP) — At least one person was injured and police made nine arrests when a protest over George Zimmerman's Florida acquittal turned violent in Oakland.

Newspapers report that a waiter guarding windows at a restaurant was hit in the face with a hammer late Monday night, and protesters threw fireworks at police in riot gear. Police deployed flash-bang grenades.

Police spokeswoman Johnna Watson says the arrests were for crimes including assault with a deadly weapon and vandalism.

The Oakland Tribune reports that the waiter's co-workers were helping him ice his head as they waited for an ambulance.

Witnesses told the newspaper that a protester was also injured after being struck by a police projectile. Police did not immediately respond to a request to confirm or deny that report.