Police said an officer and three others, including the gunman, are dead after a shooting at Chicago's Mercy Hospital. Chicago Mayor Rahm Emanuel said a doctor and a pharmaceutical assistant were the other victims.
Anthony Guglielmi, a Chicago police spokesman, identified the slain officer as Officer Samuel Jimenez.
Guglielmi said the gunman was killed, but it's unclear if he took his own life or was killed by police. In a later tweet, Guglielmi called it a "domestic related active shooter."
A massive law enforcement presence was seen on the campus and medical staff were seen being evacuated after the first reports of the shooting. Guglielmi had urged citizens to avoid the area. The hospital tweeted the shooting is over and said Chicago Police Department has secured the facility and the patients are safe.
Witness Hector Avitia told CBS Chicago he was inside the hospital waiting for test results for his wife when he saw a gunman outside in the parking lot, dressed in black, fire on someone on the ground multiple times.
Avitia said an officer arrived on the scene in an SUV and the gunman fired at the officer. He said he saw the gunman reload, fire again at the person on the ground and then go inside the hospital where more shots were fired.
He said the gunman was carrying a handgun with multiple clips.
Witness Steve White told CBS Chicago he was waiting in the emergency room when he saw the gunman outside firing on a person on the ground, who he described as a woman wearing hospital scrubs.
"He was like, he didn't care about nobody, or nothing," White said.
He said the gunman ran inside, and he could hear more shots fired. White said a police sergeant ran into the emergency room with his gun drawn and told everyone to evacuate amid a chaotic scene.
"Why would you go in a hospital and kill some innocent people, man?" White said. "I've never seen anything like this in my life."
Watch Breaking News Videos: