A Vermont man accused of murdering his mother during a fishing expedition off the coast of New England in a scheme to secure a multimillion dollar inheritance has died while awaiting trial, federal authorities said Thursday.

Nathan Carman, 29, was facing fraud and first-degree murder charges in connection to the death of his mother Linda Carmen. He was scheduled to go on trial in October.

Federal prosecutors on Thursday filed a motion to dismiss the murder-on-the-high-seas case against Carman, of Vernon, Vermont, noting the government had  “received information from the U.S. Marshal that Carman died on or about June 15, 2023.”

Carman was discovered at 2:33 a.m. at the Cheshire County Jail in Keene, New Hampshire, where he was being held in federal custody, according to Doug Iosue, superintendent of the Cheshire County Department of Corrections. Iosue said Carman was the only occupant of the cell.

He didn’t provide a cause of Carman’s “unexpected and untimely” death, but said it is under investigation by the Keene Police Department and that the cause of death would be determined by the medical examiner.

A spokesperson for the Keene police declined comment.

Nathan Carman accused of killing mother, grandfather

Prosecutors accused Carmen of planning to kill his 54-year-old mother on a fishing trip off the Rhode Island coast in 2016. While his mother was never seen again and is presumed dead, Carman was found in a life raft days later by the crew of a passing freighter ship.

Carman had been long suspected by his family and others of killing his mother and shooting to death his grandfather, wealthy real estate developer John Chakalos, in 2013.

Police said Carman was the last person to see his grandfather alive and owned a semi-automatic rifle similar to the one used to kill Chakalos. But the rifle had disappeared.