A 16-year-old boy has been charged with murder and aggravated sexual abuse in Florida in the death of his 18-year-old stepsister on a Carnival Cruise ship, the U.S. Justice Department said Monday. The teen, identified by the government as T.H., was initially charged as a juvenile on Feb. 2, but the case was sealed until U.S. District Judge Beth Bloom ordered that he would be prosecuted as an adult. Anna Kepner had been traveling on the Carnival Horizon ship in November with her family. Before the ship was scheduled to return to Florida, her body was found concealed under a bed in a room she was sharing with two other teens, including the younger stepbrother.