The "disturbing" and unreasonable actions of the officer, a two-year veteran of the department, were not within policy, Sacramento police said in a statement.
The officer was already on unpaid administrative leave as a result of the incident and will now be subject to a criminal investigation.
The department also released a second video of the incident, shot from the officer's dash camera at a much greater distance than the video shot by a bystander that circulated earlier Tuesday. The latest video has sound.
In the exchange on a residential street, the man says the officer stopped him "for nothing," then says, "If you were a real man, you would take your gun away and fight me like a real man."
The officer then lunges at the man and tackles him, punching him repeatedly. Another officer joins the struggle soon after.
The man was handcuffed for resisting arrest and for an outstanding misdemeanor warrant in Fresno County. Police said he continued to resist by kicking the inside of the patrol car and had to be restrained with a leg hobble.
But after a review, police found no charges were called for and the man was set free.
The names of the man and the officer have not been released.
Sacramento Mayor Darrell Steinberg also criticized the officer.
"I find the actions of this officer extremely disturbing, and they are not representative of the training nor the expectations we have for our police department," Steinberg said.
The incident began after the officer told the man from his police cruiser to stop after he was seen jaywalking, but the pedestrian ignored the officer, the police department said.
The officer then got out of the car and tried to detain the man, but he walked away, the statement said, adding that the two argued and the man took off his jacket and challenged the officer to fight.
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