Mayor Rahm Emanuel is huddling with Chicago Police Superintendent Eddie Johnson at city's public safety headquarters where they're monitoring the events, according to the mayor's spokesperson Eddie Johnson.
Chicago police department said there are "multiple victims" following the shooting, which happened around 3:30pm on Monday. Guglielmi tweeted that he was in critical condition but receiving excellent care.
Two people were killed, including a gunman, and an officer was critically injured after an active shooter incident at a South Side hospital, according to WGN.
The Chicago Fire Department called an emergency medical services Plan II and sent at least 10 ambulances to the scene.
He said a police officer had been shot and was in a critical condition.
Shooting reported at Chicago hospital
Police spokesman Anthony Guglielmi says officers are searching the hospital.
Mercy has a rich history as the city's first chartered hospital.
'I don't know what happened, ' she said. Employees and patients at the clinic locked the doors and hid in the back.
'This was very close to me. Police were asking people to avoid the area.
Television footage showed several people, including some wearing white coats, walking through a vehicle park with their arms up.