Police had received several complaints about a suspicious vehicle in the area, Lang said, and pulled the car over because it fit the description.
The incident is one of three Atlanta-area police-involved deaths this weekend.
DeKalb County police officer Chester Lamb, 43, was shot five times Sunday morning before returning fire and killing his assailant at a Stone Mountain apartment complex. Lamb was in serious but stable condition Sunday. The assailant was identified as Frederick Farmer, who was in his 20s, Lang said.
In Gwinnett County, George Mann, 53, of Stone Mountain became unresponsive and died after police stunned him with a Taser, Lang said. Mann's neighbor had to called 911 to report Mann was locked in the neighbor's garage, "was irate and possibly armed."
The GBI investigates shootings by police officers from most of the state’s local law enforcement agencies.
“A thorough investigation will be conducted to determine what occurred” in the Newton County case, Lang said, “and when the investigation is complete it will be turned over to the (district attorney) for any action she deems appropriate.”