DOUGLASVILLE -- A man shot six people Saturday afternoon, killing four of them, including his ex-wife and several children before turning the gun on himself on a quiet, suburban Atlanta street, police and neighbours said.

Horrified neighbours called police and tended to the severely injured victims as best they could before rescuers arrived.

The shooting happened around 3 p.m. in a housing development about 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 his own family, including several children who tried to flee, Daniel 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.

Investigators 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 law enforcement.

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.

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," Carter said. "And then I heard four more shots."