Officers responded to Wilson Boulevard after a 911 caller reported shots fired at 11:35 p.m.
When officers arrived, they found Derrick Mayes lying in the street with a gunshot wound to his torso.
Mayes, 21, was pronounced dead at the scene and was taken to the Office of the Suffolk County Medical Examiner, where an autopsy will be performed.
Detectives are asking anyone with information on this case to call the Homicide Squad at 631-852-6392 or anonymously to Crime Stoppers at 1-800-220-TIPS.
All calls will be kept confidential.