The officer fired two shots when the man charged at him, said Cedric Alexander, the public safety director of DeKalb County.
But given that the man was not carrying a weapon, the police department immediately turned over the case to the Georgia Bureau of Investigations for an independent probe.
"What I have requested here [is] a result of what's going on currently across this country as it relates to police shootings," Alexander told reporters.
The officer was white; the deceased man was African-American, Alexander said.
The incident took place Monday afternoon at an apartment complex in Chamblee, a suburb of Atlanta.
Someone called 911 to report a man "acting deranged, knocking on doors and crawling around naked," Alexander said.
When the officer arrived, the man charged at him, Alexander said.
"The officer called him to stop while stepping backward, drew his weapon and fired two shots," he said.
The man, struck twice in the upper body, died. Police later learned he was a resident at the complex.
"I can only reasonably assume that if he was running around the apartment complex naked, I believe we can make the assumption there may have been some mental health experience that he might have been having," Alexander said.
Mental health training
DeKalb County police officers undergo some degree of training on how to deal with the mentally ill. But this, and other incidents, highlight the need for more, the public safety director said.
"That's becoming more and more apparent," Alexander said. "We have already, as many departments have begun to do, look at how to expand our mental health training when we find it certainly necessary to do so. Because it appears that we're seeing more and more of these cases across the country in which police are engaging with those who appear to be in distress."
Police did not release the officer's name, but said the seven-year veteran was placed on administrative leave. During the incident, the officer had access to his stun gun and pepper spray, Alexander said. Why he chose to draw his weapon will come out during the investigation.
"I think in all fairness we need to wait and see what the outcome of the investigation is because I can't tell you, beyond what I have told you so far, what kind of measures that officer may have taken," he said.
As fatal police shootings come under increased scrutiny in the current climate, police departments also appear to be more forthcoming in proactively releasing information for transparency's sake.
Such is the case in Madison, Wisconsin, where Madison Police Chief Mike Koval has been out front and outspoken about the shooting death of 19-year-old Tony Robinson at the hands of an officer. And it seems to be the case in this DeKalb County incident.
"If you look at the state in this country and the things we're going through right now across this country with police-involved shooting, certainly it's a concern to many Americans. And there has certainly been recommendations that have been made in regards to moving towards more independent type of investigations," he said.