The Florida teenager accused of killing his stepsister aboard a Carnival cruise ship last year has been taken into the custody of the U.S. Marshals and will be held behind bars ahead of his upcoming trial.

The 16-year-old suspect, identified in court filings by his initials as “T.H.,” was ordered to report to the federal courthouse in Tampa earlier Monday morning, where his family would deliver him to the U.S. Marshals’ custody.

T.H. was indicted as an adult by a federal grand jury on charges of murder and aggravated sexual abuse in the November 2025 killing of his stepsister, 18-year-old Anna Kepner. He has pleaded not guilty to first-degree murder and aggravated sexual abuse.

Prosecutors alleged that the stepbrother “sexually assaulted and intentionally killed” Kepner on the Carnival Cruise ship Horizon while the ship was en route to Miami. The Florida high school senior died from mechanical asphyxiation, officials said. 

Prosecutors had argued T.H. should be held behind bars ahead of his trial because he is allegedly too dangerous for such a lax arrangement. His lawyers countered he’s a child who has been cooperative with the investigation and has shown no indication of hurting anyone in the months since his stepsister’s killing.

The judge ultimately directed an examination of potential options for his detainment in the Tampa area, and has now ruled for that custodial transfer to occur. 

ABC News has reached out to T.H.’s attorney for comment.

The federal trial is set to begin on Sept. 8.

Anna Kepner’s father, Chris Kepner, is married to the suspect’s mother, Shauntel Kepner.

“We would like to thank the FBI, the United States Attorney’s Office, and the U.S. Marshals Service for their assistance in helping place the accused murderer of Anna Marie Kepner behind bars until trial,” the Kepner family said in a statement to ABC News on Monday. “It was painful for our family to know that he had been free for as long as he was. We are now at peace knowing that he will not be able to harm anyone else while awaiting trial.”

The family noted that Kepner’s birthday was this past weekend.

“While birthdays are never the same without her, we continue to honor her memory and cherish the love and joy she brought to our lives,” the family said. “As we move closer to the start of the trial in the coming months, we remain hopeful for a swift conclusion to this process and for justice to be served.”