Allen is 6 feet tall, 205 pounds and has a lighter complexion, according to police. He was last seen wearing khaki pants, a white shirt and black shoes.
South Fulton police Detective Partrena Smith said Obrielle's mother and Allen are friends. Officers are actively searching for the two.
“They’ve been out all night searching, looking and canvassing the area,” Smith said.
Anyone with information is asked to call South Fulton police at 470-809-7311.
Tipsters can remain anonymous, and be eligible for rewards of up to $2,000, by contacting Crime Stoppers Atlanta at 404-577-8477, texting information to 274637 or visiting the Crime Stoppers website.