Mount Prospect police said officers responded to a 911 call for a crash involving a pedestrian in the 1300-block of Elmhurst Road around 1:56 p.m.
Witnesses told investigators that someone driving a black Chevrolet hit a person in a wheelchair who was crossing the street.
"I didn't see the car, but all I heard was just an engine taking off," witness Bobby Hansford said.
By the time Hansford ran to the corner of Elmhurst Road near Millers Road, he said the car was already gone and a badly injured man was abandoned in the road, bleeding, and separated from the wheelchair he uses to get around.
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Witnesses said the driver did not stop and continued driving south with damage to the vehicle's front end and windshield.
"I ran over to help him with three other people," Hansford said. "I went up to him and just made sure he was breathing. He was breathing, but he wasn't moving so, my roommate kept directing traffic and that's all we could do."
He said bystanders diverted traffic while a few others scrambled to help the man who'd just been hit.
"He was in bad condition. He just laid there and seemed like unconscious," Hansford said. "We didn't want to move him, didn't want to do anything."
The man was taken to Advocate Lutheran General Hospital in Park Ridge with serious injuries. Police said the driver who hit him sped off without stopping.
"Just kept going. Couldn't make out a license plate or anything. I couldn't believe that," Hansford said.
"This has always been a bad place right here because we have a trail here that crosses a busy road," said Scott Miller, who lives nearby.
Police said they were able to locate the black Chevy and its driver in an apartment complex near Elmhurst Road and Oakton Street shortly after the crash.
The southbound lanes of Elmhurst Road were shut down for hours as police scoured the area.
Police continue to investigate. So far, no citations or charges have been filed.