Officer Richard Francis, 60, was pronounced dead at Illinois Masonic Medical Center a little over an hour after the 2 a.m. shooting, according to the Cook County medical examiner's office.
The suspect in the shooting was also taken to Illinois Masonic, where she was reported to be in critical condition after being shot by responding police officers. She has not been identified.
"Our focus right now is on his family. It's a tragic loss for his family; it's a terrible loss for the Chicago Police Department," police Superintendent Jody Weis said.
Weis said Francis, a 27-year veteran, noticed the woman was engaged in a disturbance early Wednesday morning and stopped to investigate. A struggle ensued, and the woman allegedly got control of Francis' weapon and shot him in the head, police said.
Other officers responded to the shooting, and when the woman threatened them with the weapon, they shot her, Weis said.
"He was a conscientious and professional officer who will be remembered for the dedication and commitment to duty that he showed throughout his career," Mayor Richard Daley said in a release.
Francis had received several commendations throughout his career as an officer and his time serving with the U.S. Navy, Chicago police said.
He is the first Chicago police officer shot and killed in the line of duty since 2002. An off-duty officer was shot and killed in February 2007.