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The shooting took place about 5:30 p.m. at the westbound I-80 entrance to Interstate 355 in New Lenox, state police said.
One person was taken to a local hospital with life-threatening injuries, police said.
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The victim later died, police said.
Westbound I-80 at LaGrange Road was shut down, while police investigated.
Later, two lanes were closed, but some traffic was getting by.
It is not immediately clear what led up to the shooting.
Chopper 7 was over the scene about 6:30 p.m., and two vehicles could be seen in the area.
New Lenox police said there was a large police presence around Liberty Junior High School, which had parent-teacher conferences Monday night, and near Francis and Marley roads.
New Lenox police helped Illinois State Police take a suspect into custody without incident.
There has been no threat to the community, New Lenox police said.