An 18-year-old man from New York's Long Island was arrested Wednesday and charged in the murder of a 16-year-old student who was stabbed outside a pizza shop earlier this week.

Police charged Tyler Flach of Lido Beach, N.Y., with second-degree murder in connection with the death of Khaseen Morris. Flach will be arraigned on Thursday morning, Nassau County police officials said.

LONG ISLAND HIGH SCHOOL STUDENTS RECORDED ATTACK INSTEAD OF HELPING STABBED TEEN WHO LATER DIED, COPS SAY

Morris was stabbed once in the chest during an after-school fight Monday near Oceanside High School. Flach was allegedly one of about eight from a nearby high school. The fight may have been in retaliation for Morris spending time with one of their ex-girlfriends.

Police said between 50 and 70 teens watched the bloody brawl, at least some of them recording the fight on their cell phones, all while failing to do anything to defend Morris from his attackers. Morris was rushed to a hospital where he died, Newsday reported.

“Kids stood there and didn’t help Khaseen,” Detective Lt. Stephen Fitzpatrick of the Nassau County Police Department said at a news conference Tuesday. “They videoed his death instead of helping him.”

“Kids stood there and didn’t help Khaseen. They videoed his death instead of helping him.” — Lt. Stephen Fitzpatrick, detective with Nassau County Police Department

Also Wednesday, Nassau County police assigned extra officers to Oceanside High School in response to a threat made against the school.

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Hundreds attended candlelight vigils Tuesday and Wednesday evening held in the parking lot where the fatal brawl took place, Newsday reported. A second teenager was hospitalized with a broken arm and swelling to his head after Monday’s fight.