MIAMI (AP) — 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 ruled that he would be prosecuted as an adult at the request of prosecutors. Court records indicate that his defense lawyers did not object to this decision.

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 her younger stepbrother.

The cause of Kepner’s Nov. 6 death was determined to be mechanical asphyxia, when an object or physical force obstructs breathing. Kepner was a high school cheerleader at Temple Christian School in Titusville, Florida, located about 40 miles east of Orlando. At her memorial service in November, family members encouraged attendees to wear bright colors instead of traditional black “in honor of Anna’s bright and beautiful soul.”

Prosecuting teens in federal court is quite rare. T.H. was seen at the Miami courthouse in February, wearing a ball cap and a hoodie pulled tightly around his face. However, his status at that time was not fully disclosed due to his age, which prevented public disclosures by his attorneys, the government, or the court.

A judge on Feb. 6 mandated that T.H. must wear an electronic tether while residing with an uncle. This order was later amended to permit him to temporarily work with his father in a landscaping business, as per court records. Experts believe the case is in federal court, given that Kepner died in international waters, distinguishing it from typical state courts where such cases would usually be handled.