LOS ANGELES — The police here were preparing for another night of protests on Tuesday, and community activists were working to maintain the peace after anger over the acquittal of George Zimmerman in the shooting death of Trayvon Martin turned violent in South Los Angeles on Monday night.

A group of about 150 mostly young people broke away from a peaceful demonstration on Monday in the Crenshaw district, long home to many of the city’s black residents. Protesters ran through the streets, blocking traffic, hitting cars, assaulting pedestrians and ransacking businesses, the police reported.

Hundreds of police officers in riot gear descended on the area to quell the unrest. Fourteen people were arrested, the police said, half of them juveniles.