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PITTSBURGH (AP/KDKA) – The FBI is reviewing a violent arrest recorded by a bystander and posted to Facebook, which has one Pittsburgh officer involved on temporary desk duty.

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The FBI says Friday it’s trying to determine whether a civil rights violation potentially occurred during Tuesday night’s arrest of 47-year-old Daniel Adelman, of Ravenna, Ohio. If so, the FBI will launch a full investigation.

Adelman acknowledges drinking but says he just tried to help an officer who appeared to be in trouble while arresting another man outside PPG Paints Arena. Police say Adelman interfered in that arrest and Officer Andrew Jacobs has acknowledged punching Adelman repeatedly to subdue him.

The city is conducting an internal investigation as is its Citizen Police Review Board.

The DA’s office says it won’t conduct a “parallel” investigation as long as the FBI is involved.

Mayor Bill Peduto spoke publicly about the horrible scene caught on camera for the first time Friday.

“My reaction was just like everybody else’s: it looks bad,” he said.

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But the mayor says he doesn’t want to rush to judgement and says we should wait to see and hear all of the evidence.

“I’ll wait to make final judgments, and I’ll allow the investigations to continue without any pre-judgement,” he said.

Community activists fear this could hamper gains made in police-community relations.

“I don’t know how anyone could justify with… how many police officers were present? Four or five?” activist Tim Stevens, of Black Political Empowerment Project – Pittsburgh, said. “One is literally taking the head of a citizen and beating that head onto the cement.”

The incident is raising questions about whether Pittsburgh Police are getting the proper training.

“It’s not as if these are happening on a monthly basis, and they don’t seem to be happening on a widespread amount,” Peduto said. “The second part of that is we have been monitoring the number of complaints coming against our officers and those have been down 50 percent.”

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(© Copyright 2017 CBS Broadcasting Inc. All Rights Reserved. The Associated Press contributed to this report.)