Javier Soto is accused of shooting the uncle of a woman whose baby shower he was attending at a Bay Shore home.
Suffolk District Attorney Ray Tierney says that a fight broke out at the party before guests were able to break it up.
The 16-year-old then allegedly shot the uncle twice - one bullet hitting the victim's leg, which required emergency surgery.
Soto was arrested on the day of the shooting and faces several charges, including criminal possession of a weapon.
He is being held without bail and is due back in court on Nov. 14.