The manhunt is ongoing for the mass shooting suspect, 24-year-old Deion Patterson, Atlanta police said at a news conference Wednesday afternoon. Police said the gun has not been recovered.

The shooting, which unfolded in a medical center waiting room, killed a 39-year-old woman, police said.

The four injured victims, who are all women, are "fighting for their lives," Atlanta Mayor Andre Dickens said. They are ages 71, 56, 39 and 25, police said.

"As soon as possible I'll be in touch with the families of the victims," he said.

Patterson's family is cooperating with the investigation, police said.

Patterson joined the Coast Guard in July 2018 and was discharged from active duty in January 2023, the Coast Guard said.

Dr. Timothy Simons was performing surgery one floor above the scene where the shooting unfolded.

He told ABC News he completed the surgery and then sheltered in place.

When police came to clear the building floor by floor, Simons said he was told to put his hands up to verify that he was not the shooter.

"Then they escorted us all down the stairs," he said.

-ABC News' Janice McDonald

As Atlanta police search for the suspected gunman, 24-year-old Deion Patterson, they say a car was stolen "not long after the shooting" and has since been recovered.

"We are working to locate the carjacked vehicle and to determine whether it is connected to the shooting," police said.

Dr. Ahmed Ali, a radiation oncologist at the building, told ABC Atlanta affiliate WSB that he was returning from his lunch break when he saw armed officers swam the scene.

"I was worried what was happening," he said. "Building security … they told me gunshots were coming from the 11th floor. They said there was a pool of blood in the elevator shafts when the doors opened."

-ABC News' Ivan Pereira