CHICAGO (CBS) -- Thirteen people, including a 3-year-old boy, were injured late Thursday when someone opened fire in a park on Chicago's South Side, police tell CBS Chicago station WBBM-TV.
The boy was in critical condition. Investigators told the station he was shot in the cheek, and that he was at the park with his mother.
Relatives tell WBBM he is expected to live.
The other victims were listed in good to serious condition, and one has already been released from the hospital.
The shooting comes nearly three weeks after Chicago saw an outburst of violence over the Labor Day weekend that ended with eight dead and 20 others injured.
The city's Police Department has responded to shootings that have grabbed national headlines by stepping up its crime-fighting efforts, paying overtime to add patrols to some hard-hit neighborhoods, including the Back of the Yards, where Thursday's shooting took place.
Officer Amina Greer said the latest shooting occurred shortly after 10 p.m. According to Greer, at least 10 ambulances responded to the scene, transporting victims to several area hospitals. One victim transported himself to a hospital, police said.
Investigators say the shootings may have been gang-related.
The Chicago Tribune reports the people in the park were among 18 shot citywide in a span of less than four hours. One of them died.
A witness, Julian Harris, told the Chicago Sun-Times dreadlocked men fired at him from a gray sedan before turning toward Cornell Square Park and firing at people in the area. He said his 3-year-old nephew was wounded in the cheek.
"They hit the light pole next to me, but I ducked down and ran into the house," he said. "They've been coming round here looking for people to shoot every night, just gang-banging stuff. It's what they do."
Other reports said the gunman or gunmen were on foot.
Police spokesman Ron Gaines says victims are being interviewed to determine the circumstances of the shooting, adding no one had been taken into custody.
Francis John, 70, said she was in her apartment when the shooting occurred. She said she went down to see what was going on and "a lot of youngsters were running scared." She said she was surprised by what had happened, saying she has lived in the neighborhood for 30 years.
She told the Sun-Times there hasn't been much gun violence in the neighborhood in recent years, adding the neighborhood went from good to bad 10 years ago, to better recently.