Chicago police say they have launched an investigation into an incident that involved an officer picking up and slamming a man to the ground during an arrest in the afternoon of Thanksgiving. The body-slam was caught on video and it appears to show the man’s head landing on the curb.

The video practically begins with the body-slam, but police say the officer carried out what they characterized as “an emergency take down” after the man spat on him.

Chicago’s mayor, Lori Lightfoot, said that even though “a single video does not depict the entirety of the interactions between the police and the individual,” she acknowledged that “this particular video is very disturbing,” In a series of tweets, Lightfoot vowed that police would carry out a thorough investigation “so that the public may gain a complete picture of what happened.”

Police say the man, who was drinking alcohol in public at around 4 p.m., resisted several attempts to be taken into custody and licked the officer’s face, spat in his eye and mouth, and threatened him. The person who recorded the video said that she saw the officer snatch the man’s beer away and then pick him up and slam him to the ground while he was on the phone. “I was nervous. I was scared. I was hoping this young man was okay,” said Jovonna Jamison. She also insisted that the man who was detained “didn’t do anything aggressive—he just stood there.” The man was hospitalized and released into police custody “sometime overnight,” according to a police spokesman.