Donovan Lawson (YouTube)

A shocking video shows an NYPD officer beating a young man over the head with his baton at a Brooklyn subway station.

The man, 20-year-old Donovan Lawson, had “doubled up” with his friend; he went through a turnstile in the same swipe at the friend. Lawson sat down on a nearby bench, and that’s when, according to witness Marielle Anas, the officer started throwing punches.

“The kid wasn’t doing anything — that’s why I started recording,” Anas said to the NY Daily News. “If he can’t subdue this kid — he wasn’t even resisting that much!”

Anas filmed the incident as others gathered around and several people shouted at the officer to stop. “Everyone was horrified,” Anas said. “There were at least 30 or 40 people that gathered. It just seemed so obvious that it was unnecessary violence.”

When the officer hit Lawson across the head with his baton, blood sprayed from the head wound onto onlookers. “It was one of the most awful things I’ve ever seen,” Anas said. “I have blood all over my jeans. The brutality of the nightstick — it was crazy. It looked like his head exploded. I couldn’t believe I was seeing it happen.”

Anas says she tried to get the officer’s badge number, but other officers barred her from doing so as they tried to clear people away from the scene.

Lawson was hospitalized for his head wound and was arrested on charges of fare beating, resisting arrest, disorderly conduct, obstructing government administration and harassment.

The officer was reportedly also hospitalized for hand and arm injuries.