A gunman killed three people, including a police officer, at a hospital in Chicago, authorities said on Monday.
The gunman had opened fire at Mercy hospital on the city’s South Side.
Chicago police said it was with “profound sadness” that it announced the death of PO Samuel Jimenez after a “senseless active shooter incident”.
Separately, the medical examiner said it had been notified of four deaths.
It had emerged earlier that the shooter was killed; it is not clear if the shooter was killed by police or took their own life.
CNN quoted anonymous law enforcement officials saying the shooter was a 32-year old man.
A witness named James Gray told reporters that it looked as if the attacker “was turning and shooting people at random”.
The shooting apparently began as the suspect was walking with a woman near a parking lot. He turned and repeatedly shot the woman in the chest. He then entered the hospital and continued firing, Gray said.
The two had been talking to each other. Gray said it didn’t seem like a heated exchange.
“Then once she fell to the ground, he stood over her and shot her three more times,” he said.
Jennifer Eldridge was working in a hospital pharmacy when she heard three or four shots that seemed to come from outside. Within seconds, she barricaded the door, as called for in the building’s “active shooter” drills. Then there were six or seven more shots, now much closer, just outside the door.
“I could tell he was now inside the lobby. There was screaming,” she recalled.
The door jiggled, which Eldridge believed was the shooter trying to get in. Some 15 minutes later, she estimated, a Swat team officer knocked at the door, came in and led her away. She looked down and saw blood on the floor but no bodies.
“It may have been 15 minutes, but it seemed like an eternity,” she told a reporter.
Mercy has a rich history as the city’s first chartered hospital. It began in 1852, when the Sisters of Mercy religious group converted a rooming house. During the civil war, the hospital treated both Union soldiers and Confederate prisoners of war, according to its website.
The Associated Press contributed to this report