Police were in the process of arresting about 100 Occupy protesters for failing to disperse Saturday night, hours after officers used tear gas on a rowdy group of demonstrators who threw rocks and flares at them and tore down fences. Police Sgt. Christopher Bolton said the arrests came after protesters marched through downtown Oakland a little before 8 p.m. Saturday, with some of them entering a YMCA building. Meanwhile, about 100 police officers surrounded City Hall while others were swept the inside of the building to see if any protesters broke in.