A man shot six people, killing four of them, including his ex-wife and several children before turning the gun on himself on a quiet, suburban street outside Atlanta.
Horrified neighbours called police and tended to the severely injured victims as best they could before rescuers arrived.
The shooting happened around 3pm local time in a housing development west of Atlanta, Douglas County Sheriff's Lt Glenn Daniel said.
The shooter, whose name was not immediately released, appeared to have targeted his ex-wife and her household, including several children who tried to flee, he said.
The authorities did not release the names of the victims because they were still trying to contact the next of kin.
Investigators believe the gunman killed himself at the end of the shooting spree. They were still trying to determine the shooter's motive and piece together what happened.
"I've been in law enforcement out here 20 years and this is the worst I've ever seen," Mr Daniel said.
He did not know when the couple divorced or if they had prior contact with police.
Teresa Carter, 59, said she heard the gunfire from inside her home but did not see what happened. Police said victims were shot inside and outside the home.
Ms Carter said she often saw the children playing in the driveway and around the neighbourhood. They enjoyed petting her dog.
"I heard shots, and I heard the girl scream," she said. "And then I heard four more shots."