Nearly a decade after Liliana Moreno and her 8-year-old daughter Daniella disappeared in the Miami area, federal investigators say they have now arrested a man in the case: the girl’s father.

Gustavo Alfonso Castaño Restrepo, 55, of Miami, was arrested Monday, days after he was charged in federal court with one count of kidnapping resulting in death in connection with the 2016 disappearance of Liliana and Daniella, shows show court documents.

But much of the case remains a mystery to the public and Liliana’s family: Although the two-page indictment filed in U.S. District Court in Miami lays one charge against him (accusing him of kidnapping Liliana, then of 42 years old), alleges that the kidnapping led to the death of both Liliana and the child. Authorities have released very few details, including why investigators believe they are dead, how the kidnapping occurred, what led them to arrest Castaño and whether they know the motive.

The prosecution’s claim that Liliana and Daniella are dead “is not what we want to see,” Liliana’s brother, Eduardo Moreno, told CNN this week.

“We as a family… are trying to figure out what happened,” he told CNN by phone.

The mother and daughter, who lived in Doral, northwest of Miami, were last seen at or near a Home Depot in nearby Hialeah on May 30, 2016, according to the FBI.

Castaño is Daniella’s father, although “he was never involved in Daniella’s life,” Eduardo Moreno told CNN.

Liliana and Castaño also met through their careers, her brother said. Liliana was an architect, Castaño was in construction and they had worked together often, the Miami Herald reported.

The U.S. Attorney’s Office for the Southern District of Florida announced the charge Tuesday. Castaño remained in custody following a hearing before a federal judge that day, the office said.

Court documents and the office’s news release do not say whether investigators found Liliana or Daniella dead. The indictment alleges that Castaño kidnapped Liliana, held her “for reward or otherwise” and used “a cell phone, the Internet, a motor vehicle and the Homestead Extension of the Florida Turnpike” to commit the crime.

“It is further alleged that the commission of the aforementioned kidnapping resulted” in the deaths of Liliana and Daniella Moreno, the accusation says, without providing further details.

The FBI, one of the agencies investigating the case, according to prosecutors, cannot discuss ongoing investigations like this one, said spokesman Jim Marshall, who pointed to court documents and the U.S. attorney’s news release as the information available. The Miami-Dade Police Department, another agency involved in the case, did not respond to CNN’s request for comment.

CNN reached out to the US attorney’s office for questions about the case but did not immediately receive a response.

An attorney for Castaño, Phil Reizenstein, told CNN on Friday that he had just been retained in the case and needed time to investigate, prepare and craft a bond proposal. His office intends to request that a remand hearing be held on Wednesday, he said.

If convicted, Castaño would face a mandatory minimum sentence of life in prison, according to the statement from the U.S. Attorney’s Office. The maximum penalty would be death, the office said.

the disappearance

Eduardo spoke to his sister on the phone less than an hour before she left their house on May 30, 2016, he told CNN. He did not say why he left the house, but added that Liliana’s intention was to stay home most of the day.

That day was also the birthday of his sister Carolina, who lives in Colombia with much of the rest of the Moreno family, he said.

“They always called her (Carolina) on her birthday,” Eduardo said. But Liliana and Daniella did not call Carolina that Monday.

That’s when his family started to worry.

Eduardo, who was in Colombia at the time, said the family received a call from Castaño on the morning of May 31 asking if they had heard from Liliana. During the call, Castaño doubted whether he had last seen Liliana on May 30 or days before, Eduardo said.

Increasingly concerned about his sister’s whereabouts, Eduardo asked a friend of Liliana’s who lived in Doral to check his sister’s house to see if she was there, he said.

“We assumed that Liliana’s car was not at her house, because Gustavo told us that he had looked for Liliana’s car and it was not there,” Eduardo said. But Liliana’s friend said that her car was parked in the same place it used to be parked and that no one was home.

Eduardo then decided to involve the police.

At Liliana’s home, police saw her car in the driveway and food on a stove, and they also found her wallet, CNN affiliate WPLG reported.

The FBI missing persons poster for the mother and her son says they were “reportedly last seen at or near the Home Depot located at 13895 Okeechobee Road in Hialeah, Florida.” According to WPLG, Castaño told police that Liliana had asked to drop her and her daughter off on the Florida Turnpike at Okeechobee Road, an intersection very close to Home Depot.

“We want to know what happened,” Eduardo Moreno told CNN. “If something happened to my sister Liliana, where is Daniella?”

“In this case, it’s more about finding out what happened or at least trying to bring them back,” he said.

CNN’s Amanda Musa contributed to this report.

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