Iran Press/America: The video shows a man lies motionless after his head hits the pavement. The man was taken to hospital and was said to be in a stable condition.
The incident was filmed by a citizen named 'Jovana Alexiss Jamison', who said the incident happened at about 16:00 local time (10:00 GMT) on Thursday, CNN reported.
Ms. Jamison said the man didn't do anything aggressive, he just stood there, according to the Chicago Sun-Times.
"He was standing there using his cellphone. They took away his bottle of liquor and threw it," she said.
The policeman is now being investigated by the Civilian Office of Police Accountability.
Meanwhile, police claimed that he performed an 'emergency takedown' after being threatened.
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