A 3-year-old boy was among 12 people hit by gunfire at a park in the Southside of Chicago on Friday. The other victims included a 15-year-old boy and a 17-year-old girl.
Deputy Fire Chief James Mungovan said all of the victims were alive when they were taken to hospital. The child, Deonta Howard, was struck near his ear, with the bullet exiting through his cheek, and was said to be in a critical condition.
The boy's grandmother, Semecha Nunn, told the Chicago Tribune that he would need plastic surgery. At least six more people were shot, one fatally, in five more attacks elsewhere in the city on the same evening, police said.
The spate of shootings follows the US national Labour Day holiday weekend - the first in September - when eight people were shot dead in Chicago and a further 20 injured. Among those killed on Labour Day was Deonta's uncle, Jerome J. Money Wood, a local rapper.
The authorities have said previously that gun violence in Chicago has slowed since last year, when 500 homicides were reported in the city. The incident comes within days of the mass shooting at Washington DC's Navy Yards, in which 12 people were killed including the gunman, Aaron Alexis.
It has been revealed that Alexis was vetted for security clearance by the same firm that conducted a background investigation of the whistle-blower Edward Snowden.