Kane Millsaps, 16, is facing up to 20 years in prison for the brutal attack on his unsuspecting 12-year-old victim. Disturbing footage of the attack was posted online in the days following and quickly gained thousands of views.

Millsaps pleaded not guilty to first-degree battery and possessing an instrument of crime in court on June 3. Police say he hit the boy while wearing brass knuckles.

In the 23-second video, Millsaps swears at the camera while wearing a set of brass knuckles on his left hand. He then walks up to the boy – seen chatting with friends while standing on a skateboard – before punching him in the face.

His victim crashes to the ground with his hands covering his face. The attack took place on May 31 at a park in Conway, in Arkansas, USA. A police statement read that Millsaps hit the victim for “running his mouth saying he was an MMA Fighter and he could beat him up”.

The victim told authorities he did not know Millsaps. Officers learned of the attack after a witness’ family member brought the video to the Conway Police Department on June 1. When officers spoke with the victim, they noted his right eye was bruised, there was a cut on his neck and he had broken teeth.

The victim said he lost consciousness after being hit and “when he woke up he thought he had gravel in his mouth but it was pieces of his teeth”, according to the statement. A witness – who filmed the incident on Milksops’ phone – told investigators the victim “did not see Millsaps coming and did not know he was going to be hit”.

Millsaps was arrested on June 2 at the Faulkner County Sheriff’s Office Juvenile Services division after meeting with his probation officer. Defense Attorney Frank Shaw represents Millsaps, who is set to appear in court next Aug. “The video is disturbing,” Shaw said. “It caused me – like everyone else that saw it – a good bit of discomfort.”