The shooting happened just before 10 p.m. Wednesday on Dartmouth Street in Hempstead.
The victim, identified by family members as Dante Quinones, was apparently standing with a group of kids at the time. They scattered before officers arrived, sparking a search for witnesses and suspects.
The sound of the gunfire was first picked up by the town's Shot Spotter system. Then police received a flood of calls about shots being fired.
Quinones was rushed to Winthrop University Hospital, where he was pronounced dead.
Police are still interviewing eyewitnesses and trying to figure out the events that led to the shooting.
At this point, there are no arrests.