Anna Kepner’s aunt is speaking out after the 18-year-old was found dead on a Carnival Cruise shi.

Anna, of Titusville, Fla., was found dead under a bed aboard the Carnival Horizon on Nov. 8. A death certificate obtained by PEOPLE states she died from being “mechanically asphyxiated by other person(s).”

While there have been no arrests made, court papers filed in the custody proceedings between Anna’s stepmother, Shauntel Hudson, and her father, Christopher Kepner, suggest that Anna’s 16-year-old stepbrother is under criminal investigation.

Reacting to her niece’s death, Anna’s aunt, Krystal Wright, told Fox 35 Orlando, “I know Anna fought. I know she fought for her life.”

“We don’t understand why, if the boy is a suspect, why has he not been charged yet? What’s happening there?” she continued, referring to Anna’s stepbrother.

Calling the tragedy “rough,” Wright added that she and her family continue to grow frustrated over not knowing what happened to Anna, as well as what the next steps in the investigation will be.

“It’s a turmoil. We’re just sitting here waiting,” she told Fox 35 Orlando.

An autopsy determined that Anna died from asphyxiation from a bar hold — or an arm held across the neck, per ABC News.

The teenager had been traveling on the cruise ship with her father, stepmother, siblings, stepsiblings and other family members when she died. Anna shared a room with her two stepsiblings on the ship.

After reports surfaced about his stepson being a potential suspect in Anna’s murder, Christopher told PEOPLE, “I cannot say that he is responsible, but I can’t decline.”

“He was the only one that was in the room, and the FBI has an ongoing investigation, in which they will have to provide the evidence to say that he did do it or did not do this,” he continued.

The FBI has not publicly named any suspects at this time.