Wauconda police and fire crews responded just before 10:25 a.m. to the pond, near Garland Road and Main Street in Wauconda, for a report of a vehicle upside-down in the water.
Wauconda fire crews got the man out of the black 2010 Ford Edge within 10 minutes, but he was pronounced dead on the scene, police said.
The man's identity was not immediately released.
Witnesses said they saw the car traveling north on Main Street before hitting the curb at Garland, and landing upside-down in the pond.
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Some raced to the scene to try to help the man.
Shirley Wojcicki and her husband, Ross Gemmill, were going for a walk in their Wauconda neighborhood, when a loud noise made them stop.
"We turned around, as we heard a splash in the pond," Wojcicki said.
Gemmill ran into the shallow water to try to help.
"I told my wife to call 911, and I ran over there. There was a car upside-down in the pond -- heartbreaking," Gemmill said.
Gemmill said he could see the driver, who was unresponsive.
"He said, 'he's trapped in here. I can't open the door,'" Wojcicki said.
Gemmill was soon joined by other witnesses, who tried unsuccessfully to break the car's windows.
"We're pounding on the door, 'hang in there, guy, hang in there. We're getting help any minute. Hang in there,'" Wojcicki said.
Wauconda divers searched the pond and did not find any other victims, police said.
"So frustrating to try to get that door open, and we couldn't do it. He was right there," Gemmill said.
Wauconda's police chief was not surprised to hear residents sprang into action.
"We have an outstanding community, and we have an excellent police/community relationship in our community," Chief Dave Wermes said.
The Lake County Major Crash Assistance Team and Wauconda police are investigating the incident.
An autopsy is scheduled for Thursday morning.
Wauconda police said in a Facebook post just after 11:20 a.m. that some roads were closed during the investigation. They have since reopened, and the car has been pulled from the water.