The shooting happened around midnight at what deputies called "a large gathering" in the park, located about 85 miles southeast of Atlanta. Investigators say the gathering appeared to be a birthday celebration.
The victims include four 18-year-old men, two 18-year-old women and five 17-year-old boys, the sheriff's office said. An 18-year-old man and a 17-year-old boy were listed in critical condition. The rest were stable.
A night meant for celebrating turned into a mass casualty scene, with nearly a dozen young people caught in gunfire at a public park. The sheriff's office has not released details on a shooter or a motive. It remains unclear what led to the violence.