The incident happened around 7 p.m. inside the Fogo de Chão Brazilian Steakhouse in the 3100 block of Piedmont Road NE, just north of East Pace Ferry Road, FOX 5 Atlanta reported.
Atlanta police Deputy Chief Charles Hampton Jr. said a restaurant employee called 911 to request assistance handling an "unruly" patron and officers arrived to find the armed man in the front bar area. Witnesses said the man had become "rowdy" and was drinking straight from a liquor bottle.
The man was asked to leave but refused, a scuffle ensured between him, officers and the restaurant security guard. An officer deployed a Taser on the man, but it was ineffective, Hampton Jr. said.
Police said the man drew his gun and fired one shot at the security guard, striking him. An officer returned fire and shot and killed the man. The guard was transported to a hospital in stable condition.
Patrons described ducking for cover beneath tables as the shots rang out during dinner.
"My husband heard some commotion, and he said 'I need you to hit the floor,' and he snatched me out of the chair," one woman told FOX 5 Atlanta. "And all the sudden, everyone is just stepping over each other, babies are crying, and family, parents are laying on top of babies."
"That is so unfortunate that that is what our world is coming to, and it's almost like 'where do you go to find safety?'" the patron said. "We come here quite often looking for a nice, peaceful atmosphere, and we've always had that until tonight."
No one else was hurt, and the Georgia Bureau of Investigation is investigating the shooting.
"There were a lot of individuals inside the restaurant, but our officers did a great job to isolate the subject to the front of the business, where no patrons were in harm’s way," Hampton said.
Authorities have not yet named the deceased man, but The Atlanta Journal-Constitution reported family identified him as 22-year-old Nygil Cullins, a former employee of Fogo de Chao.
His mother told the newspaper her son struggled with mental health and that she called 911 hours before the shooting to get him to the hospital, but he left home before first responders could arrive.
"I would have rather him be in a psychiatric hospital as opposed to him being outside in a body bag," she said.