Officials said they believe the shooting started after a fight broke out inside the event center.
Police did not release any information on possible suspects.
This was the second shooting at a graduation party in Georgia in a week. Investigators believe at least 50 gunshots were fired the previous early Saturday morning when a graduation party in a Fayette County neighborhood swelled to nearly 200 guests, most of whom were not invited, The Atlanta Journal-Constitution previously reported.
Deputies were called about 12:20 a.m. when multiple shots were heard in the area. Two people were injured in the Fayette County incident.