An NYPD officer is seen on newly released cellphone video apparently knocking out a Brooklyn teen who had been stopped on suspicion of smoking pot, sources told The Post.

Police say that the Internal Affairs Bureau is probing the incident, in which the officer allegedly pummels Marcel Hamer, 17, on June 4th in Clinton Hill as the teenager pleads with the officer, telling him that he was only smoking a cigarette.

“Mister, it was just a cigarette, sir,” Hamer can be heard saying on the video.

“It was just a cigarette.”

As the officer notices a person videotaping the incident, he taunts the individual, “Yeah, get it on film.”

Although the alleged knockout blow is not seen, the teen appears to be unconscious at the end of the footage.

“You knocked him out!” one of Hamer’s friends could be heard saying.

The teen’s family said he now suffers neurological problems, according to The Brooklyn Paper.

Hamer was charged with disorderly conduct in connection with the incident.