An undercover police officer, who had been marching with demonstrators, aims his gun at protesters after some in the crowd attacked him and his partner in Oakland, California on Wednesday. The man was identified as an officer with the California Highway Patrol, according to the Oakland Police Department.

Police said more than 100 demonstrators marched through Oakland and Berkeley, which has a history of social activism, to protest grand jury decisions not to indict white police officers in the deaths of two unarmed black men. Under cloudy skies, turnout was smaller than earlier in the week, when demonstrators in the area threw rocks at police and shut down a major freeway.

A police officer holds back demonstrators as an undercover officer makes an arrest in Oakland, Calif. NOAH BERGER / Reuters

—Reuters