A teenager near New York City was stabbed to death in an attack witnessed by dozens of onlookers — some who rolled video of the slaying rather than help stop it, police said Tuesday.

Khaseen Morris, 16, and a friend were set upon by as many as a half-dozen people Monday in an after-school brawl that stem from a dispute about a girl.

The incident happened in front of a pizzeria in a strip mall parking lot in Oceanside, a Long Island community about 30 miles east of Manhattan, authorities said.

Morris was stabbed in the chest, and a 17-year-old friend suffered a broken arm and swelling to his head, police said.

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According to NBC News, authorities announced an arrest in the fatal stabbing on Wednesday. Tyler Flach, 18, was charged with murder in connection with the death of Morris, Nassau County police said in a statement. He will be arraigned Thursday.

Investigators believe at least 60 teens had gathered around the parking lot to watch the confrontation, and some took cellphone video that was posted on social media.

“Kids stood here and didn’t help Khaseen,” Fitzpatrick said. “They’d rather video. They videoed his death instead of helping him.”

Nassau County Executive Laura Curran said Wednesday that additional police officers will patrol Oceanside High School and neighboring schools and that the county reached out to the Oceanside School District to ensure they have the mental health resources to support students in need.

“I want to plead with all our residents — not just our young people: if you see someone in serious danger, please use your phone to get help — not likes and shares,” Curran said in a statement.