Occupy Wall Street (& Beyond): LiveStream from Clashes at Occupy Oakland
UPDATE 1537 GMT: A slightly different view of the incident. The video starts with a police officer, via megaphone or sound system, telling the protesters that if they do not disperse they will be arrested. One could ask why that is necessarily? The protesters appear to be in a penned-off street, with the police on the other side of the barricades.
After a few seconds, the tear gas is fired, along with flash grenades. A few protesters appear to hold their ground. Towards the front of the pack, on the right hand side, a man who may already be leaving, is apparently hit my a flash grenade, or shrapnel of some kind, and falls backwards, in the direction that the majority of the crowd is moving. When protesters notice that he is injured, they move forward to help, or remove him, and a police officer, who first aims a weapon (tear gas gun?) at the crowd, throws at least 1 flash grenade into the crowd:
UPDATE 1507 GMT: This narrated video appears to show a police officer throwing a flash grenade into a crowd of people in Oakland as they try to help a wounded protester. While the video starts after the tear gas has been fired, and after the protester was initially wounded, it is clear that the crowd was helping the protester, and did not pose an immediate threat to the wall of police standing nearby: