The attack is now underway! Note that there is still no one in the intersection. Note further, that it would have been impossible for the main body of demonstrators to hear any dispersal order, since the police are still hiding around the corner.
Video of Police attacking demonstrators at this intersection. Video: Real Player required - Excerpt from "This is What Democracy Looks Like" Copyright 2000 by IMC/Big Noise Films, original footage courtesy of Headwater Action Video Collective