A Michigan man facing charges for the murder of his three sons in 2010 will remain in custody, with a judge setting his bond at $60 million on Monday.

John Skelton, aged 53, appeared in a Lenawee County courtroom for his arraignment on three murder charges. Authorities suspect that Skelton is responsible for the deaths of his sons—Andrew, 9; Alexander, 7; and Tanner, 5—sometime between November 25 and 26, 2010. Despite extensive searches, the boys have never been located, as reported by the Detroit News.

Just last week, Skelton was charged with the murders, ahead of his anticipated release from prison after serving a 15-year sentence for unlawfully imprisoning his sons.

At the time of the boys’ disappearance, their mother, Tanya Zuvers, had sole custody amid divorce proceedings with Skelton. The boys had spent Thanksgiving with their father, and their mother was scheduled to collect them the following day.

Throughout the investigation, Skelton offered various accounts of what happened to the boys, including a claim that he handed them over to an organization to protect them from their mother, whom he accused of abuse—allegations that Tanya Zuvers has vehemently denied.

FBI Special Agent Corey Burras said John Skelton searched online about how to break a neck, potassium cyanide, and rat poison. The searches were allegedly conducted the same month his sons disappeared.

The FBI agent also alleged that John Skelton addressed Zuvers in a suicide note, stating, “You will hate me.” Burras said he believed the note implied that he killed their sons.

John Skelton appeared virtually at March’s hearing to declare his sons legally dead. He did not provide any information about their whereabouts.

“I’m at a disadvantage. Anything I say isn’t going to make a difference,” he said.

In March, a judge granted Zuvers a petition to have her three sons declared legally dead. However, the judge ruled there was insufficient evidence proving they were murdered on or about November 26, 2010, or that their father killed them.

A probable cause affidavit from early November stated that state police interviewed John Skelton, but he became uncooperative and refused to disclose this sons’ whereabouts. The document stated that he has been “inconsistent and misleading” for the past 15 years, according to the Detroit News.

A preliminary hearing is scheduled for December 1.