Four people were killed and two others were injured Wednesday in an exchange of gunfire between a group of man and store employees, authorities said. Police said the shootings Wednesday night at a variety store on the South Side killed three men, including one of the gunmen, at the scene. A 17-year-old boy died later at an area hospital, police said. The two injured people were being treated at local hospitals. Police said the store was heavily damaged by gunfire, and the shootings were still under investigation.