CHICAGO (CBS) — An off-duty Chicago Police Officer shot and wounded a man outside a Northwest Side restaurant last night.

The officer has more than a decade with the Chicago Police department, says police union spokesman Pat Camden.

He was off-duty – at a restaurant in the 43-hundred block of West Fullerton with his girlfriend and family – when two men started causing a disturbance, Camden says.

And the officer told the men who he was – and escorted them outside.

“One was holding a knife and threatening him with a knife. The officer didn’t do anything at that point.

“The second individual went to the trunk of his car and came out with a handgun. As the individual turned and pointed the handgun at him, the officer defended himself (and) opened fire. He hit the subject in the leg.”

Camden says the men managed to get away in a car – but police arrested them not far away.

The man who was shot was treated at a hospital.

The Independent Police Review Authority is investigating the shooting by the officer.

As of last night, Camden says, investigators were still trying to find the gun the man pulled on the officer.

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