The shooting took place inside a facility of the Northside Hospital.
A gunman opened fire inside a medical building in the US city of Atlanta leaving one dead and four injured, the Atlanta Police Department said in a series of tweets. The suspect, identified as 24-year-old Deion Patterson, was arrested several hours after the shooting.
He was seen with a gun in his hand in CCTV footage and had carjacked a vehicle to flee the scene, police said.
Patterson, a former US Coast Guardsman, was taken into custody north of the city in suburban Cobb County, several hours after shooting at Northside Medical.
Chief of Police Darin Schierbaum said in a press conference that all the victims are women and that the shooting occurred in the waiting room of the hospital. Mr Schierbaum indicated that the shooter's mother was among the people in the room but was not a victim of the shooting.
Earlier, Atlanta Police posted four photographs of Patterson on Twitter to warn residents. He is seen walking into an office doorway and raising his arm to point what appeared to be a handgun. The image does not show what he might have been targeting.
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Three people have been hospitalised, while a fourth has been declared dead.
Police identified the suspect as Deion Patterson who is still at large.
Northside Hospital said in a tweet that they are cooperating with the authorities.
"Northside Hospital is cooperating with law enforcement following the shooting at our midtown #Atlanta location earlier this afternoon. We urge people in the area to shelter in place and follow instructions from law enforcement on the scene. This tragedy is affecting all of us, and we ask for patience and prayers at this time," the hospital said.
Atlanta Mayor Andre Dickens said in a tweet that he was in contact with police and advised people to in the area to shelter in place. "I am in close contact with the Atlanta Police Department as they are responding to the active shooting situation in Midtown near 1100 W Peachtree. Those in the area should shelter in place," he said.
About an hour after the gunfire, a SWAT team gathered near the High Art Museum, about 3/4 of a mile (1.21 km) from the shooting scene, according to a video posted on Twitter by a local CBS affiliate.
Atlanta Public Schools said several schools in the were put into temporary lockdown "out of an abundance of caution", Reuters reported.
There have been more than 180 mass shootings -- defined as four or more people wounded or killed -- so far this year in the United States, according to the Gun Violence Archive. With more firearms than inhabitants, the United States has the highest rate of gun-related deaths of any developed country: 49,000 in 2021, up from 45,000 the year before.
The White House said President Joe Biden and Vice President Kamala Harris had been briefed on the Atlanta shooting. Spokeswoman Karine Jean-Pierre said the president's hands were tied on "more steps to deal with the violence that we're seeing in our communities or schools or churches."
"American people should be able to feel free to go into a grocery store, to go to church," Jean-Pierre said.