Tyler Flach, 18, is accused of second-degree murder in the deadly after-school brawl that broke out not far from the victim's Long Island school.
Police said that most of the "50, 60, 70" kids who witnessed the attack on Khaseen Morris did nothing to stop it.
"That's egregious," said Detective Lt Stephen Fitzpatrick.
"Kids stood here and didn't help Khaseen," Lt Fitzpatrick said. "They would rather video this event."
Police were called to a row of shops near Oceanside High School in Nassau County on Monday afternoon.