The shooting happened yesterday in a housing development west of Atlanta, Douglas County Sheriff's Lt. Glenn Daniel said.
Horrified neighbours called police and then tried to help the severely injured victims as best they could before rescuers arrived.
The shooter, whose name was not immediately released, appeared to have targeted his ex-wife and her household, shooting victims inside and outside the house, Daniel said. Several children were gunned down as they fled on a street, neighbours said.
Authorities did not release the names of the victims because they were still trying Saturday to contact the next of kin. Investigators believe the gunman killed himself at the end of the shooting spree.
Police 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," 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. Carter said she often saw the children playing in the driveway and around the neighbourhood. They enjoyed petting her dog.

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