Chicago police said Friday that they have opened an investigation after a viral video showed a police officer slamming a man onto the ground.

Anthony Guglielmi, the chief communications office for the city’s police force, said the actions of the officer depicted in video were under investigation and “complaints of citizens are being taken very seriously.”

The widely-shared incident was posted to social media and shows an officer picking up a 29-year-old man and throwing him to the pavement on the city's South Side, hitting his head on the sidewalk curb in front of a bus station.

Another officer is seen trying to shake the man but he does not appear to stir in the remaining moments of the 42-second clip.

Police said that the officer’s body slam was “an emergency take down” in response to the man licking an officer’s face, threatening him and spitting in his eye and mouth, The Chicago Tribune reported.

An arrest that occurred in the 700 block of E. 79th is under investigation tonight as actions depicted on a social media video & the complaints of citizens are being taken very seriously. https://t.co/PL35f2as5O pic.twitter.com/B46haaMP0m

— Anthony Guglielmi (@AJGuglielmi) November 29, 2019

Mayor Lori Lightfoot (D) wrote on Twitter that the video is “very disturbing,” but noted that it does not depict the entirety of the interactions between police and the individual.

“The matter is under investigation by the Civilian Office of Police Accountability (COPA). It is my expectation that the investigation will be comprehensive and expedited so that the public may gain a complete picture of what happened,” Lightfoot wrote.

The matter is under investigation by the Civilian Office of Police Accountability (COPA). It is my expectation that the investigation will be comprehensive and expedited so that the public may gain a complete picture of what happened.

— Mayor Lori Lightfoot (@chicagosmayor) November 29, 2019

Jovonna Jamison, the bystander who filmed the video, told the Tribune that she was in a car at a red light when she saw the officer take the man’s beer.

“I was nervous. I was scared. I was hoping this young man was okay,” Jamison said.

She said that witnessing the officer’s action left her “hysterical.”

“I’m not really surprised because it happens so much in Chicago, but I didn’t think I would ever see it front and center,” Jamison told the newspaper.

Chicago’s Civilian Police Oversight Agency (COPA) tweeted that it was “actively seeking witnesses, canvassing for 3rd party video and obtaining evidence related to this incident.”

COPA is also actively seeking witnesses, canvassing for 3rd party video and obtaining evidence related to this incident. If anyone has additional information or video pertaining to this incident please call 312-746-3609 or visit https://t.co/209nWge2P7 for more information (2/2).

— COPA (@ChicagoCOPA) November 29, 2019