Two young men arrived at the restaurant and confronted Kaleb Duckworth, 19, around 10 p.m. Sunday, according to police.
The fight grew out of a dispute on social media, Duckworth’s dad, Tommy Duckworth, told FOX 5 Atlanta Thursday.
"Got them bickering, and that fraction of a second changed the lives of everybody," he said.
Daniel Lee Roberts, 20, has been charged with aggravated assault and battery for allegedly throwing the punch that knocked Duckworth out – but additional charges are likely now that the victim has died.
The fall left him hospitalized in the intensive care unit with severe brain trauma, according to a crowdfunding account set up for the family by his mother’s coworkers. Police said he also suffered a severe cut to his face and broken bones.
Duckworth turned 19 on Saturday, according to FOX 5. He celebrated with a river float day with family and friends.
"He could have spent it with his friends but he came to us and asked us to go with him," his mom, Amanda Duckworth, told the station.
"I didn't realize at the time that was the last day I would have with him," Tommy Duckworth added.
In other interviews with local media, the parents remembered their son as an "All-American" teen who loved to spend time in his truck, outdoors and fishing.
"He was just a little country boy with a heart of gold and he’d give anybody the shirt off his back," Amanda Duckworth told the Dawson County News.
He was also an organ donor.
At around 2 p.m. Thursday, hospital workers gave his remains an honor walk before going into surgery that could potentially save up to five lives, according to Rikki Lynn Anderson, who organized the crowdfunding effort.
Roberts was being held on a $60,000 bond.