An Oakland man says a police officer shot him with a rubber bullet or beanbag while he was videotaping last week's standoff between law enforcement and a small group that took over a building and lit fires after a day of peaceful anti-Wall Street protests.

Experts in police use of force who reviewed the footage Scott Campbell captured say it appears the volley was unprovoked and inappropriate, the Oakland Tribune reported Tuesday.

In the video posted on YouTube , Campbell, 30, is heard calling, "Is this OK?" to a line of riot gear-clad officers. He told the newspaper that he was asking if his distance from them was adequate because an officer had asked him to step back. A firearm held by an officer then is seen going off, followed by Campbell's yelps of pain.

The Oakland Police Department also has been criticized for wounding an Iraq War veteran during an Oct. 25 skirmish. City spokeswoman Karen Boyd said Tuesday that anyone who thinks they witnessed improper police conduct is encouraged to make a report with the police department's Internal Affairs division or Oakland's Civilian Police Review Board.

Officer Johanna Watson, a department spokeswoman, said Campbell's allegations already are being looked into.

University of South Carolina criminal justice professor Geoffrey Alpert said that unless something occurred off-camera to provoke the officer, the shooting was "one of the most outrageous uses of a firearm" he'd ever seen.

"Unless there's a threat that you can't see in the video, that just looks like absolute punishment, which is the worst type of excessive force," Alpert said.

Campbell, who identifies himself as an anarchist, said he took video of the confrontation that occurred early Nov. 3 because he wanted to document any instances of excessive force, but did not imagine that he would be a target.

Authorities have said they moved to arrest more than 100 people and used tear gas and beanbags after a small group of self-proclaimed anarchists entered a vacant building with bottles and flares and then lit fires in the street when officers tried to clear the building.