The argument started on Sunday after 2 a.m. at Social Bar and Grill" at 401 East Dundee Road, Wheeling police said.
Police found a 24-year-old man with gunshot wounds at the bar. He was rushed to the hospital where he died.
Witnesses told police that an altercation escalated into the shooting.
Nobody is in custody.
The victim's identity has not been released.
Anyone with information is asked to call police at 847-459-2632.
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