Berkeley County Prosecutor Catie Wilkes Delligatti released the eight-minute video to The Associated Press. The teen's face is redacted in the video, taken from a sheriff's cruiser.
The video shows two officers yanking the teen through the open driver's side window to the ground, where he lands face first and is immediately placed in handcuffs. Footage shows one of the officers then kicks and stomps him several times and puts his knee on the teen's shoulder blade, pressing down with his full weight. The officer then punches the teen at least eight times.
A minute later, the teen is pulled up to his feet but remains limp as he is thrown further to the side of the road.
Gov. Jim Justice has said the incident "cast a dark shadow" on law enforcement.
Authorities originally denied media requests for the video, citing the investigation.
Troopers Michael Kennedy and Derek Walker and a sheriff's deputy were fired in January. Another deputy who was fired recently got his job back.
Kennedy, 29, of Morgantown, was indicted Wednesday by a federal grand jury on one count of deprivation of rights under color of law - language used to describe crimes committed by police officers while on duty.
The indictment accuses Kennedy of using excessive force resulting in bodily injury.
The teen was treated at a hospital and released.
State police have said the teen was involved in a crash with a sheriff's cruiser before a pursuit ensued, his vehicle crashing again before he was apprehended. Delligatti said she couldn't release details on whether the youth was charged, saying juvenile prosecutions are sealed.
The American Civil Liberties Union's West Virginia chapter has said it would look into whether the teenager's civil liberties were violated.
"The brutality witnessed in this video is shocking but all too familiar," said Loree Stark, the West Virginia chapter's legal director, in a statement. "Law enforcement has a constitutional responsibility to avoid excessive force, and it is crucial for videos like this to come to light so that offending parties will be held accountable."
Walker also faces an excessive force lawsuit filed last year by a Charles Town attorney who says the trooper dragged his wife and slammed her to the ground in 2016 while she was talking to construction workers about a sidewalk project. State police responded to the scene when a worker allegedly backed his truck into the driver's door of her SUV in a parking lot.
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