The second officer was badly wounded and was being treated at a local hospital, Athens-Clarke police Capt. Clarence Holeman told The Associated Press.
The gunman fired a shot into Senior Police Officer Elmer "Buddy" Christian's patrol car, killing him, according to a statement released late Tuesday by Athens-Clarke police.
The wounded officer, Senior Police Officer Tony Howard, underwent surgery Tuesday, police said.
The shooting took place at the entrance to the Cascades on the River apartment complex on Sycamore Drive in Athens, on the city's west side.
Athens-Clarke police swarmed an area off Atlanta Highway in a massive search for the shooting suspect after the gunfire was reported around 1:30 p.m. Tuesday, the Athens Banner-Herald reported.
Police were searching house-by-house for a suspect, whom they describe as a 33-year-old man.
Authorities were also looking for a silver Geo Prizm with Georgia plates. Police said they found the vehicle on the other side of town, off Winterville Road, around 5:15 p.m. but the suspect remained at large.
Five schools and a pre-kindergarten program in the area were locked down Tuesday afternoon as a precaution while police searched for the suspect, whom they described as armed and dangerous.
The Clarke County School District canceled all Tuesday night events in the schools since the suspect was still at large.