The shooting happened in the northbound lanes of I-94 at 73rd Street around 2:40 a.m.
An unknown person was shooting from a car on the expressway when a bullet struck a 7-year-old boy.
The boy was a passenger, the driver pulled over at 22nd and Michigan to call for help, ISP said.
The boy to a local hospital by firefighters. At last check he was in serious condition, according to the Chicago Fire Department.
Northbound lanes of the Dan Ryan at 71st Street were closed during the investigation. All lanes were reopened by 5 a.m.
No other information was immediately available.
It is unknown if anyone was in custody.
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