The Cook County state's attorney's office had charged 18-year-old Eugene Bailey, but authorities announced Monday they've dropped the charge and he's being released from custody.
Three other teens are still facing charges in the melee captured on a cell phone video.
The video shows a group striking 16-year-old Derrion Albert with boards and kicking him as he lay on a sidewalk.
Albert was a sophomore at Christian Fenger Academy High School in Chicago.
Bailey's aunt, Desiyan Bacon, has said her nephew didn't have anything to do with the beating and was friends with the victim.