Joe Hendrix, 34, of Ooltewah, Tenn., told the Walker County, Ga., sheriff's department he shot Ronald Westbrook outside his rental home in Chickamauga, Ga., after giving the elderly man several "verbal commands" Westbrook did not respond to, Sheriff Steve Wilson told reporters.
In retrospect, his lack of response was likely due to his advanced Alzheimer's disease, Wilson said in comments reported by the Chattanooga (Tenn.) Times Free Press.
When Westbrook was shot, he was clutching letters he had taken from a nearby house where he previously lived, the sheriff said.
No charges were filed against Hendrix as of early Friday, but that might change after all the evidence is reviewed, Lookout Mountain Judicial Circuit District Attorney Herbert Franklin said.
Georgia's 2006 "Stand Your Ground" law, which lets people use deadly force to protect themselves, "may apply to this case," Wilson told reporters.
Westbrook rang the doorbell where Hendrix and his fiancee live around 4 a.m. The couple moved into the subdivision about two weeks ago, a neighbor said.
The fiancee, whose name was not released, called police and stayed on the phone with an emergency dispatcher who sent two sheriff's office patrol cars to the residence.
After a 9- or 10-minute wait, before deputies arrived, Hendrix went outside armed with a .40-caliber handgun and saw the elderly man in silhouette behind the house, Wilson said.
"There was no light except for the front porch light," he said.
Fearing for his safety, Hendrix fired four shots, with one bullet hitting Westbrook in the chest, killing him, the sheriff said.
"In my personal opinion, I believe that he should have stayed inside the house," Wilson said of Hendrix. "Did he violate any laws by exiting the house? No."