The boy was entertaining the public with his dance moves at around 11.30pm near Independence Street in Cape Girardeau, Missouri, when the attacker crept up behind him.
He had been dancing on the street to hip hop music coming from a speaker when a black car pulled up close, a Facebook live video posted on Friday night shows.
Out of the car, a man emerges and dances up behind the boy while appearing to go along with the performance.
The boy peered back at the man and turned his head forward again, continuing to dance.
The man "runs up behind the juvenile who is dancing and violently punches the juvenile with extreme force in an unprovoked attack," Cape Girardeau police Sgt. Joey Hann said in a statement to The Sun on Monday.
A man who got out of a car crept up behind the dancing boy and punched him in the face
A man watching the boy dance ran after the suspect, who escaped in a car.
The victim, who is 12 years old, fell to the ground and started bleeding from a wound to the head, Hann stated.
The video shows the boy sitting on the street corner for about 10 seconds, grasping his face, before standing up and bending down in obvious pain.
Friends of the boy took him to a local hospital, where he began recovering, police said.
"He was able to tell officers at the hospital that he did not know the suspect and he and his friends did not have any disputes that would have led to this encounter," Hann stated.
After the boy was hit, a man sitting on the sidewalk shouted, "Hey!" and ran after the suspect, but it was too late as the perpetrator got in the car and sped off.
The man who unsuccessfully chased the suspect identified himself to TMZ as Michael "Crank" Curry and the person who posted the video on Facebook.
Curry said the victim is named Ethan and goes by the nickname Eman.
The victim and a shorter boy in the video who witnessed the attack are students at Curry's local dance studio, according to TMZ
Hann stated, "This is a cowardly and disgusting act of inexcusable violence on one of our public streets and The Cape Girardeau Police would like to ensure that this suspect is safely apprehended.”