Four people were killed and three wounded in a shooting early on Saturday at an illegal gambling club in New York City, police said.

The six men and one woman were shot just before 7am in a building in the Crown Heights neighborhood of Brooklyn.

Chief of detectives Dermot Shea said four men were dead at the scene and the others were taken to hospitals with injuries that were not life-threatening.

The victims, who were not identified, ranged in age from 32 to 49, Shea said at a briefing. Two may have lived out of state and the rest were from neighborhoods throughout Brooklyn, Shea added. One additional person was injured while fleeing.

No arrests had been made and police did not know the motive for the shootings, Shea said. He said two guns were found at the scene and more could potentially be found.

Mayor Bill de Blasio said on Twitter that the city “awoke to senseless gun violence”. The Democrat added: “I’ve said it before and I’ll say it until I can’t anymore: we have an epidemic of gun violence that spares no community – and it won’t stop until we get guns off our streets once and for all.”

The shooting was the second mass killing in New York in a week in a city that has seen a marked drop in homicides in recent years. Four homeless men were beaten to death by another homeless man on 5 October in the Chinatown neighborhood. In 2000, there were more than 600 homicides in the city. Last year, there were fewer than 300.

A sign on the building where the bloodshed occurred said “Triple A Aces”. Shea said there was “evidence of gambling” including cards and dice inside.

The gambling operation was unlicensed but police had not previously received any complaints about the location, chief of patrol Rodney Harrison said.

Crime scene tape surrounded the building and investigators in white jumpsuits could be seen going in and out. The block where the shots rang out has empty storefronts and boarded-up buildings as well as renovated townhouses.