Gwinnett County police said the call came in at about 1:45 p.m. Saturday as a burglary in progress.
When officers arrived, they found three people inside — two men and a woman. One of the men was dead from a gunshot wound, police said. The other two occupants were not hurt, authorities said.
Police told Willis that nothing was taken from the home and that there were no signs of forced entry.
Investigators spent Saturday afternoon interviewing witnesses.
Neighbors reported suspicious activity at the home, saying recently they noticed a number of vehicles coming and going from the townhome.