Crowds turned violent in Oakland late Sunday night. We're received reports that rocks and bottles were thrown at police and that reporters were attacked by protesters. At about 8:30 p.m., police opened the intersection to traffic. But it quickly deteriorated when demonstrators surrounded frightened drivers who found themselves trapped. The crowd forced them to turn around. Oakland police officers that had been near the corner retreated, leaving the helpless drivers without police protection. It's unclear who gave that command.