The incident happened in Commack on Diellen Court at about 10 p.m. on Saturday, Aug. 20, the Suffolk County Police Department said.
Police said a mortar-style firework exploded and struck the man in the face.
He was hospitalized for treatment of serious but non-life-threatening burns and lacerations to his face and head, police said.
Detectives are asking anyone with information about the incident to call the police at 631-854-8252.
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