CHICAGO (CBS) — A Chicago police officer is under investigation, after a bar fight in the Edgewater neighborhood.

A witness said it happened at Norse Bar in the 6300 block of North Clark Street shortly after 1 a.m. Sunday.

Police confirmed an off-duty officer was involved in an altercation with a 36-year-old man, prompting an Internal Affairs investigation.

Police said the 36-year-old man was not cooperating.