A video clip is raising new questions about whether police used excessive force against Occupy Oakland participants during the fracas after last week’s general strike.

The video by Scott Campbell, 30, of Oakland, shows a line of riot-gear-clad officers at Frank Ogawa Plaza’s north end, near the foot of San Pablo Avenue. Campbell said the video was made shortly before 1 a.m. Thursday, around the time that police moved in after other protesters broke into and defaced a nearby building and erected and set fire to barricades in the street.

Campbell, holding the camera, moves slowly to his right, filming the line; Campbell is heard twice asking, “Is this OK?”

“When I was approaching the line, an officer told me to stop and step back, so I stepped back 5 or 10 feet and started filming, and I asked if that was OK,” he explained Monday.

He said there was no reply until an officer raised a weapon and fired, striking him in the upper right thigh with a nonlethal projectile; the video ends with his crying out in pain.

“At first I was just stunned, and in an immense amount of pain,” he said. “It was just shock. I was extremely shaken. And since then what I’m really wondering is what was going through that person’s head that made him think it was OK to shoot another person with a less-than-lethal weapon for doing absolutely nothing wrong.”

Oakland police and City Hall representatives didn’t return emails seeking comment Monday.

Geoffrey Alpert, a University of South Carolina criminal justice professor who’s an expert in police decision-making and use of force, said the video left him “astonished, amazed and embarrassed.”

“Unless there’s something we don’t know, that’s one of the most outrageous uses of a firearm that I’ve ever seen,” he said. “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.”

Campbell said his friends saw him get hit and rushed him away to the shelter of a doorway. Someone brought an ice pack while a legal observer took down information, and then his friends helped him get to a taxi. He saw a doctor later Thursday, who told him to keep the wound bandaged and iced. He said Monday he has a 1½ -inch wound with swelling and bruising around it.

Campbell said he does social and digital media work for a local nonprofit and supports Occupy Oakland. “I don’t camp out there, I’ve been a participant but not an active organizer,” he said. “I’ve come out for general assemblies and marches, and I came out that day for the general strike to show my support.”

He said he brought his camera that night to document any excessive force used by police, never imagining that might make him a target. “I don’t know if I was in the right place at the wrong time or the wrong place at the right time.”

He said he wants an independent, not internal, investigation of this and other reports of excessive force, and is considering whether to take legal action.

“I’ve been discussing it with some individuals from the National Lawyers Guild. So far nothing’s been decided,” Campbell said. “It’s shocking that someone who is a police officer felt it was appropriate to do that. I’m not sure what the options are, but I would like to have the officer identified, and I would like for him to be held accountable.”

“It looks terrible,” agreed Sam Walker, a professor emeritus of criminal justice at the University of Nebraska, Omaha, who consulted with Oakland police on the federal consent decree emerging from the Riders scandal. “It certainly looks like they singled him out to be shot … and there does not appear to have been any sort of attack by the protester. Clearly, the camera is not approaching the officers, so they couldn’t claim that he posed a threat.”

Paul Chevigny, professor emeritus at the New York University School of Law, said it looks like “a violation of his First Amendment rights apart from being a violation of his Fourth Amendment rights. He has a right to take a film of what the police do — we’ve been over this thousands of times — unless he’s interfering in some way.

“The basic problem of police retaliating against people who are trying to record what’s going on is perennial,” said Chevigny, adding this occurs all over the nation. “They (officers) consider it a kind of ‘contempt of cop.’ It’s an expression of the fact that people do not trust the police. The police read it as a criticism of them. It’s not even necessarily that they’re trying to prevent people from seeing what they’re doing.

“But this extreme version (of retaliation) is very unfamiliar to me,” he added. “I can’t imagine what they’re going to say about shooting this guy. Sounds like the Oakland police need a little brush-up on their training.”

There have been other allegations of excessive force against Occupy Oakland participants. Best known is the case of Scott Olsen, 24, an ex-Marine and Iraq War veteran struck in the head by what witnesses said was a police projectile Oct. 25. He suffered a fractured skull but is expected to recover.

Another veteran, Kayvan Sabeghi, 32, of Oakland, claims officers beat him with batons and tackled him early Thursday, then denied him medical care for hours. He underwent surgery Friday to repair a lacerated spleen.

Oakland police and Alameda County sheriff’s departments have said they’re investigating the Olsen and Sabeghi incidents.

Contact Josh Richman at jrichman@bayareanewsgroup.com and Thomas Peele at tpeele@bayareanewsgroup.com. Follow Josh Richman at Twitter.com/josh_richman. and Thomas Peele at Twitter.com/Thomas_Peele.