(CNN) -- A police officer has been shot and multiple victims have been reported in a shooting at Chicago's Mercy Hospital, the department said Monday.
Police have secured the hospital and patients are safe, the hospital said Monday afternoon.
The suspect has been identified as a 32-year-old male, according to a Chicago police source.
The injured officer is in critical condition and receiving "excellent care," Chicago Police chief communications officer Anthony Guglielmi said on Twitter.
At least one offender has been shot, Guglielmi said. It was not immediately clear if by "offender" he meant a suspect or someone else.
Witness Steven White told CNN's Ryan Young that he was in the emergency room when he saw the shooter firing at police.
"We heard some shots so we all ran to the emergency window, we see this guy out there, military style, shooting at the police -- pow, pow, pow," he said.
When White looked outside he said he saw a person lying on the ground by the main entrance. The shooter turned around and opened fire again before running inside the main entrance.
"I don't even have words to say how I was feeling," White said. "It's sad, you can't even come to the hospital for treatment."
The incident drew a heavy law enforcement response to the hospital. The FBI is assisting local authorities, a spokeswoman said.
At least 15 medic units were sent to Mercy hospital, Chicago Fire Department Public Information Officer Larry Merritt said.
Chicago Mayor Rahm Emanuel and Chicago Police Superintendent Eddie Johnson were both at Public Safety headquarters monitoring the incident, Guglielmi said.
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