Citing a statement from Atlanta police, news outlets report that 20-year-old Souleymane Diallo was arrested Thursday on charges including second-degree murder.
Family members say Sonja "Star" Harrison was an eighth-grader from Stone Mountain who was expected to give birth next month. The baby also died in the Monday shooting.
Investigators believe the gunshot went through the floor of an upstairs apartment and struck Harrison in the head. Sonja's mother, Sonja Denise Harrison, tells the Atlanta Journal-Constitution that Diallo was not the father of her daughter's baby.
Authorities have not said what prompted the shooting. It's unclear whether Diallo has an attorney who could comment.