Chicago (AFP) - A gunman opened fire Monday at a hospital in the US city of Chicago, police said, adding that there were reports of "multiple victims" including a wounded officer in "critical condition."
"Reports of shots fired in the vicinity of 26th and Michigan near Mercy Hospital. Avoid area. Heavy police response incoming," Chicago Police spokesman Anthony Guglielmi tweeted.
At least "one possible offender" had been shot and there were "multiple" other victims, he added.
"A #ChicagoPolice officer has been shot in the active shooter incident at Mercy Hospital. He is in critical condition but receiving excellent care. Please send your prayers," Guglielmi later added.
TV footage showed people filing out of the hospital into a parking lot with their hands in the air.
"We were going about our business and waiting for our results and then I heard shots fired," an unnamed witness told the local CBS affiliate.
"I turned around to my right and I see a man shooting someone on the ground, shot him multiple times.
"And then almost immediately an officer was already coming in an SUV and he exchanged fire at them and then reloaded and shot the person on the ground again and then he made his way into the hospital and more shots were fired."
The shooting came less than two weeks after a gunman killed 12 people in a California music bar packed with college students.
That rampage followed the worst anti-Semitic attack in modern US history, when a gunman opened fire on worshipers at a synagogue in the US city of Pittsburgh on October 27.
The incidents have added to the growing outcry over gun safety in the United States, where there have been more than 300 mass shootings this year.
A hospital employee quoted by the Chicago Tribune said she was in her office when a notice came over a public address system telling those in the hospital to lock their doors.
"I don't know what happened," the unnamed employee told the Tribune.
"They told us to run, so we did."