BURLINGTON, Vt. (AP) — The man charged with killing his mother at sea during a 2016 fishing trip off the coast of New England has died awaiting trial, federal authorities said Thursday. Prosecutors say it was a scheme to inherit millions of dollars.

Nathan Carman, 29, of Vernon, Vermont, was scheduled to face trial in October. He had pleaded not guilty last year to fraud and first-degree murder in the death of his mother, Linda Carman of Middletown, Connecticut.

The cause of Carman's death was not immediately clear. One of Carman’s lawyers, Martin Minnella, said he was told about Carman’s death Thursday by the U.S. Marshals Service.

“We had spoken to him yesterday. He was in good spirits,” Minnella said. “We were meeting with some experts today over Zoom at 12 o’çlock. We were prepared to start picking a jury on Oct. 10 and we were confident we were going to win. It’s just a tragedy, a tragedy.”

The eight-count indictment also says Carman shot and killed his wealthy grandfather John Chakalos at his home in Windsor, Connecticut, in 2013 but does not charge him with murder in his death.

Minnella and fellow attorney David Sullivan, both from Connecticut, where Carman grew up, had criticized the indictment, including allegations Carman killed his grandfather, saying Carman was never charged with that crime.

“The whole situation would have come out in court,” Minnella said Thursday. “It would have come out in court and I’m positive ... that this young man would have been vindicated.”

In September 2016, Carman arranged a fishing trip with his mother, during which prosecutors say he planned to kill her and report that his boat sank and his mother disappeared in the accident.

He was found floating in an inflatable raft eight days after leaving a Rhode Island marina with his mother, who was never found. Prosecutors allege he altered the boat to make it more likely to sink. Carman denied that allegation.