Ricky Bryant Jr., 26, and Eric Barker, 33, were working as security guards at the complex in what residents described as a high-crime neighborhood. They were investigating a suspicious person there when shots rang out, DeKalb County Police Chief Terrell Bolton said.
Mr. Bryant was a two-year veteran of the department, and Mr. Barker had worked there for four years. Both were married. Each had four children.
Chief Bolton called the shootings a "must-solve crime" at a news conference Wednesday afternoon and urged witnesses to come forward with information.
"Don't lie to us," Chief Bolton said. "Tell us the truth."
Chief Bolton did not say whether the officers returned fire before they were killed, and he did not say what led to the shooting.
"They never had a chance," Chief Bolton said, an indication that the shootings might have been an ambush.
County officials said a $55,000 reward is being offered for information leading to the arrest of those responsible.
"These police officers were heroes; they were committed and dedicated to law enforcement," said Vernon Jones, the county chief executive. "We will not rest until those folks responsible for this are apprehended and justice is served."
Authorities were searching for two men seen running from the scene. Police were using dogs and a helicopter to search for the suspects.
"We've got every able body looking for them," Chief Bolton said.
Later, at a news conference, Chief Bolton addressed the gunmen: "If I were you, I'd turn myself in. The sun's coming up. Before sundown, we're gonna find you."
He told reporters the dead officers were wearing their police uniforms.
Police were called to the scene about 12:40 a.m., Chief Bolton said. One officer was already dead. The other was pronounced dead at Grady Memorial Hospital in Atlanta, he said.
Schools were locked down during the investigation in the area, about six miles east of downtown Atlanta.
Patreka Anderson, a resident of the complex, said she was awakened by the gunshots but did not think anything of it because the neighborhood around the Glenwood Gardens apartment complex is a high-crime area with a lot of drug activity and prostitution.
"We always hear shooting," she said. "I didn't think that was any big deal."
Teofil Taut, who said he has owned the 176-unit complex for about two years and lives in one of the buildings, said he hired police as part-time security officers in December to keep homeless people from breaking into the apartments.
Another resident, nurse's assistant LaShawn Corbin, said she is considering moving.
"We don't expect the people who try to protect us to be hurt so seriously," she said. Ms. Corbin said she would fear leaving her children there "because the person who did it has no conscience for human life."