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.

Timothy Hudson was initially charged in February and subsequently indicted on March 10. But the breadth of the case was not known until a seal was lifted Friday, weeks after U.S. District Judge Beth Bloom in Miami said he would be prosecuted as an adult at the request of the government.

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.

The cause of Kepner’s Nov. 6 death was determined to be mechanical asphyxia, which is when an object or physical force stops someone from breathing.

“I hope he will be in custody soon. We are ready for justice,” said Kepner’s grandfather, Jeffrey Kepner, who was on the cruise.

An email and voicemail seeking comment from Hudson’s attorneys were not immediately returned Monday. Hudson has remained free in the care of an uncle since his arrest in February.

“Our hearts go out to the victim’s family during this unimaginable loss,” U.S. Attorney Jason Reding Quiñones said in a written statement. “A federal grand jury has returned an indictment charging serious offenses that allegedly occurred aboard a vessel in international waters.”

Kepner was a high school cheerleader at Temple Christian School in Titusville, Florida, some 40 miles east of Orlando. At her memorial service in November, family members encouraged people to wear bright colors instead of the traditional black “in honor of Anna’s bright and beautiful soul.”

Teens are rarely prosecuted in federal court. Hudson pleaded not guilty when he was initially charged in February, though the proceedings were not public because of his age and neither were court documents. He was seen at the courthouse wearing a ball cap and a hoodie pulled tightly around his face.

A judge on Feb. 6 said Hudson must wear an electronic tether while living with an uncle. The order was changed to allow him to join his father for a few days last week at a landscaping business, newly unsealed court records show.

Prosecutors objected to Hudson’s release, citing dangerousness, and asked a judge Monday to revisit that order now that he has been charged as an adult. Defense lawyers will have a week to respond.

“He committed these crimes against a victim with whom he had no apparent relational strife, and whom he was being raised to view as a sibling,” Assistant U.S. Attorney Alejandra López said in a court filing.