Eleven other people - including a child - were injured as a hail of gunfire erupted at Brownsville Playground in Brooklyn at around 11pm on Saturday night.
The area was teeming with locals who were out celebrating 'Old Timers Week' - an annual community block party in its 56th year.
A single shooter - still at large - is believed to be responsible for the tragedy, according to The New York Post.
Following the incident, scores of police and EMS response teams descended upon the area before victims were rushed to nearby hospitals.
Detectives were seen pacing the area, with one abandoned firearm found among discarded cups and bottles that littered the ground following the festival.