Police in Oakland, California, have arrested more than 400 Occupy Oakland protesters, as well as a number of journalists, in one of the largest mass arrests since the nationwide Occupy protests began last year. Police fired tear gas, bean bag projectiles and flash grenades. The protest began when activists attempted to take over a vacant convention center to establish a new headquarters and to draw attention to the problem of homelessness. A group of protesters later entered Oakland City Hall and caused some property damage. Protesters and Oakland officials blamed each other for sparking the violence.