Rolling Meadows police were called to the Stadium Sports Club on Algonquin Road about 11:40 p.m. for a report of shots fired in the area.
When police arrived, they found three men had been shot.
RELATED: 'American violence' took life of 8-year-old girl months after moving to Chicago from Mexico: family
Law enforcement officials said the shooting started with a fight among patrons.
Two of the three are currently being treated in local hospitals, and the third, who police said was the gunman, a 33-year-old Forest Park man, is in police custody being questioned.
The Forest Park man suffered an injury to his hand during the altercation and subsequent shooting.
A 38-year-old Des Plaines man was shot in the abdomen and is in critical condition at Lutheran General Hospital.
A 26-year-old Elgin man was shot in the leg, and has been treated and released.
Police are not looking for any other suspects, and the incident is still under investigation.