Police arrested Pedro Merchant in Valley Stream on Thursday.
Investigators say he gunned down 17-year-old Dante Quinones on Dartmouth Street in Hempstead last week.
Quinones was apparently standing with a group of kids at the time when he was shot multiple times.
The rest of the group scattered before officers arrived, sparking a search for witnesses and suspects.
Quinones was rushed to Winthrop University Hospital, where he was pronounced dead.
Merchant now faces second-degree murder charges.
A motive has not been released.
