Police immediately searched the hospital and secured the facility stating that at least one "possible offender is shot", according to police spokesperson Anthony Guglielmi.
The department issued a statement on Twitter saying there are "reports of multiple victims" after gunfire broke out on Monday afternoon.
Chicago Mayor Rahm Emanuel and police Superintendent Eddie Johnson were on their way to University of Chicago hospital, where the wounded police officer was being treated, according to local media. They appeared to know each other and were having a normal conversation.
Update: 5:04 p.m. EDT-One of the people shot during the incident was a Chicago Police Department officer.
"Once she fell to the ground, he turned around and shot her three more times".More news: Nintendo's Reggie Fils-Aime dashes hopes of an N64 Classic anytime soon
"Once he entered he just started shooting at random", Gray said.
A witness told Reuters that she heard several gunshots with pauses in between.
Correa said she was waiting in the lobby on her way up to the 12th floor, and officers told her to close the doors and stay quiet.
Moments later, Guglielmi reported one police officer was shot and is now in critical condition.
"I am scared as hell". That could have been us back there and if any bullets had pierced the wall we all would have been hurt'.