Aquil Byrd, a 12-year veteran of the force, was arrested by the Internal Affairs Unit on Wednesday.
According to investigators, Byrd was in the 3000 block of North Front Street on September 25, 2011 as officers were called to clear a large crowd.
According to the D.A.'s office, a man in the crowd argued with Byrd about moving off the street.
Surveillance video from a nearby Chinese restaurant shows the man walking inside and then, about 20 seconds later, Byrd enters as well.
Then, the D.A.'s office said, Byrd yells at the man, hits him in the face and grabs him by the throat.
That man was not arrested or charged with any offense. He reported the incident to police and Byrd was placed on administrative duty.
The case was sent to the district attorney's office for review, which approved charges for Simple Assault and Official Oppression, both 2nd degree misdemeanors.
Commissioner Charles Ramsey said he will suspend Officer Byrd for 30 days with the intent to dismiss.