UPDATE (8:35 PM EASTERN):
Chicago police officer Samuel Jimenez has died after being shot during a shooting inside a Chicago hospital on Monday. The others who were shot and the gunman are also dead, ABC Chicago is reporting.
Shots were fired both inside and outside of the hospital around 3 p.m. local time. An ER doctor was also one of those who were shot and killed.
Three people are in critical condition, including a police officer, after a shooting Monday afternoon at Chicago's Mercy Hospital, a Chicago Fire Department spokesman said.
The suspect was also shot and is in critical condition, spokesman Walter Schroeder said. The suspect has been identified as a 32-year-old male, according to a Chicago police source.
Police have secured the hospital and patients are safe, the hospital said Monday afternoon.
Earlier, Chicago Police said an officer and an offender were shot. The incident drew large numbers of law enforcement and emergency responders. Vehicles with flashing lights cordoned off the blocks around the busy medical center.
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 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.