Vermont man accused of killing mother at sea dies before trial. What we know.

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.

After Chakalos' death, Carman received $550,000 as a beneficiary of bank accounts his grandfather had set up. Carman was unemployed and low on funds when he planned the fishing trip with his mother in 2016, according to prosecutors.

Prosecutors alleged the deaths were part of a scheme to inherit an estimated $7 million of the $42 million Chakalos left to his four daughters.

A federal grand jury last May indicted Carman on eight charges accusing him in his mother’s death as part of an effort to defraud insurance companies. The indictment accused Carman shooting his grandfather at his home in Windsor, Connecticut, but did not charge him with murder in his death.

The inheritance remains in probate court, where Carman's three aunts sued to block Carman from receiving any money from his grandfather’s estate.

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Family, attorneys saddened by news of death

Carman's family said they were stunned by news of his death.

"We were deeply saddened to hear of Nathan’s death this morning. While we process this shocking news and its impact on the tragic events surrounding the last several years we ask for your understanding and respect relative to our privacy," the family said through lawyer William Michael, Jr.

One of his lawyers, Martin Minnella, told the Associated Press that Carman appeared to be “in good spirits” when he last spoke to his defense team on the phone Wednesday.

“We were meeting with some experts today over Zoom at 12 o’clock. We were prepared to start picking a jury on Oct. 10 and we were confident we were going to win,” Minnella said. “I’m just heartbroken because I wanted him to have his day in court.”

Carman was found on a life raft a week after his boat sank with his mother on board

Carman's case has proven captivating since his dramatic rescue by a freighter crew a week after his 31-foot boat Chicken Pox vanished in September 2016.

That ill-fated journey was dissected at a trial before U.S. District Court Chief Judge John J. McConnell Jr. in 2019.

In testimony, Carman described discovering water in the bilge, turning the engine off, and asking his mother to pull in the fishing lines. He said the boat went under after he readied a life raft and grabbed survival gear. He did not place a distress call or alert his mother that they were in peril, he added.

“But you didn’t shout out to your mother to be prepared?” McConnell asked at trial.

“I didn’t know the boat was going down until I was in the water,” Carman answered.

“I treated my mother like a passenger,” Carman said. “She was more of a problem than a solution.”

Carman said he got into the life raft, which was equipped with 30 days of food, and called out for his mother but got no response. He was rescued, still aboard the raft, a week after he said his boat went down.

Carman filed an insurance claim weeks after the boat vanished. The insurers denied his claim after reviewing the case and Carman sued to recoup the boat's losses.

McConnell ruled in favor of the insurers in finding that it was Carman’s own faulty modifications – including removing a bulkhead and trim tabs by drilling four half-dollar-size holes in the back of the vessel – that likely led to the boat's sinking. Carman denied that allegation.

Contributing: The Associated Press

This article originally appeared on USA TODAY NETWORK: Vermont man accused of killing mother in inheritance scheme dies in jail