The suspect assaulted the girl in a gangway in the 10700 block of S. Calumet Ave around 3 p.m. Wednesday, police said.
The suspect is African American, approximately 5'10" tall with a slim build, according to a community alert. He was wearing a black hooded sweatshirt, a black ski mask, black sweat pants and gloves.
Police are urging residents not to walk alone and stay in well lit areas.
