At least nine people were shot in Philadelphia on Saturday night, leaving two in critical condition, the police said.
Multiple shooters exited a vehicle in the Kensington area of the Pennsylvania city and began shooting, firing about 40 shots, Philadelphia First Deputy Police Commissioner John Stanford told a televised news briefing.
The injured were in a hospital, seven of them in stable condition, he said.
The target of the shooters, who returned to the vehicle and left, remained unknown, Stanford said, adding that police were investigating.
The history of mass shootings in the US
The bloodshed follows a series of US school shootings that have left dozens dead and wounded this year alone, adding to a long-running US debate over gun control. One of the deadliest took place in May when a gunman killed 19 children and two adults in Uvalde, Texas.
One person was killed and about 20 wounded on Halloween night in shootings in Kansas City and Chicago.