The incident took place in the Bronx, New York, shortly after 10am on December 31.
A man can be seen on the ground at the start of the clip, as three officers – two male and one female – stand over him.
Suddenly, one of the officers swings two punches at the man’s head – connecting both times.
A few seconds later, he reaches down and slaps the man across the side of the face.
About ten seconds later, all three officers are holding the man and kneeling next to him. The same officer is then seen punching the man in the head for the third time.
The victim appeared to be bleeding from the face near when he was hit with the trio of strikes.
The video continues on for about another 30 seconds, at the end of which the man is seen on his feet being pinned against the police van as the officer who punched him spoke in his ear.
The woman who posted the video on social media wrote about what she claims she saw in the incident.
‘This man was already in his car and the police were in the van getting ready to pull off,’ Alexis Jasmin wrote on Facebook.