An Atlanta police officer charged with fatally shooting his apartment complex's security guard over the weekend was acting in self-defense, his attorney said Monday evening.

The security guard, posing as a law enforcement officer, barged into Atlanta police Officer John Kevin Freeman's apartment and tried to sexually assault Freeman's wife, defense attorney Bruce Harvey said.

Cobb County police, however, are staying mum on what led to the deadly clash early Saturday between Freeman and security guard Xavier Mallett.

Freeman, 36, a seven-year Atlanta police veteran, is accused of fatally shooting the unarmed Mallett, 37, as he was leaving a confrontation outside Freeman's apartment in the Ivy Ridge Apartments complex on Bentley Road southwest of Marietta.

Freeman is being held without bond in the Cobb County Jail on charges of aggravated assault and murder —- charges that Freeman's attorney doesn't believe are warranted.

"My understanding is that he was defending his home, his property and his family from a home invasion," he said. "Every action that he took was legally justified."

Cobb County police won't say why Mallett banged on Freeman's door shortly before 4:30 a.m. Saturday, or what the confrontation between the two men was about, Sgt. Dana Pierce said.

Mallett lived in the same apartment complex as the Freemans. Freeman's wife answered Mallett's knock, and Mallett forced his way into the apartment, Pierce said.

The commotion woke Freeman. Freeman and Mallett had a physical confrontation, Pierce said. Freeman then went inside his apartment, got a semi-automatic pistol and shot Mallett multiple times.