Her 16-year-old stepbrother faces federal charges of murder and aggravated sexual abuse, the U.S. Attorney’s Office for the Southern District of Florida said in a statement Monday. Court documents show the motion was initially filed Feb. 2 under seal, but the case was transferred to adult prosecution and unsealed Friday.

The news release refers to him only as T.H., and that is also how he is referred to in the court documents. He has been released into the custody of a guardian, but not his parents, according to court documents.

Lawyers for T.H. did not immediately respond to a request for comment.

Anna Kepner was found dead Nov. 7 while she was vacationing with her family on a Carnival Horizon cruise ship. The cruise ship returned to the Port of Miami the next day, as planned, Carnival said in a statement at the time.

The news release says that while the ship was in international waters en route to Miami, “T.H. allegedly sexually assaulted and intentionally killed Kepner.” The Miami-Dade Medical Examiner’s Office determined Kepner’s cause of death was “mechanical asphyxiation.”

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

Chris Kepner, Anna Kepner’s father and T.H.’s stepfather, told NBC News on Monday that “justice needs to be served.”

“That is where the family stands,” he continued, saying T.H. should be in custody.

He previously said in a statement that the loss of his daughter is “a pain that will never fully heal” and that his family believes in “accountability and in the importance of justice being carried out.”