A Vermont man facing federal charges for allegedly killing his mother during an offshore fishing trip in a plot to defraud his family and an insurance company is demanding grand jury minutes, according to court filings.

Nathan Carman, 29, is also accused of gunning down his grandfather John Chakalos, a World War II paratrooper and self-made multimillionaire, as part of a scheme to claim hundreds of thousands of dollars from the family trust fund.

When he ran low on cash years later, according to prosecutors, he allegedly took his mother out to sea, killed her and sank the boat.

But while he has only been charged with one count of murder in connection with the death of his mother, Linda Carman, the indictment alleges that he also killed his grandfather and "concocted cover stories to conceal his involvement" in both slayings.

VERMONT MAN NATHAN CARMAN, CHARGED WITH KILLING MOTHER LINDA CARMAN AT SEA, PLEADS NOT GUILTY

Nathan Carman in suit and tie leaving court

Nathan Carman leaves federal court in Providence, R.I., Aug. 21, 2019. In a court paperwork filed Thursday, Jan. 26, 2023, lawyers for Carman, charged with killing his mother at sea during a 2016 fishing trip off the coast of New England, asked for minutes from the grand jury proceeding that led to his indictment.  (AP Photo/Steven Senne, File)

Chakalos, the family patriarch who built a fortune of tens of millions of dollars, died in December 2013. 

According to an online obituary, his death was unexpected. Chakalos was a World War II veteran and Army paratrooper who served with distinction in the Philippines. His wife of 59 years died a month before he did.

Court filings allege that Carman shot him to death with a rifle he'd bought a month earlier.

Chakalos was described as a "self-made man" and real estate developer with a passion for philanthropy and family. 

VERMONT MAN CHARGED WITH MURDERING MOM AT SEA OVER INHERITANCE MONEY AFTER BOAT SANK OF RHODE ISLAND COAST

Linda Carman holds a fish wearing sunglasses and pink shirt

Linda Carman and her son Nathan Carman often fished together. He's accused of murdering her while at sea in 2016. (Facebook)

Carman, on the other hand, failed out of community college while his grandfather was paying for his truck and apartment, according to court documents.

When his grandfather died, Carman received about $550,000 in inheritance, according to court filings.

However, his lawyers argued that he has no idea what evidence could have been presented to the grand jury regarding his grandfather's death and added that "if what the Government presented was inaccurate or untrue, then Mr. Carman may have grounds to dismiss the Indictment."

Read the motion (App users go here)

The demand for grand jury minutes is a rare one, experts tell Fox News Digital, because such proceedings are usually secret.

"It is unusual for the defense to request grand jury minutes, because those motions are rarely granted," said Neama Rahmani, a former federal prosecutor who maintains a private practice in Los Angeles.

Nathan Carman with his mom, Linda Carman

Nathan Carman is accused of killing his mother, Linda Carman, in 2016, while at sea on a fishing trip to get his hands on her millions.  (Facebook)

"There is a strong presumption that grand jury proceedings are secret, and grand jurors can return indictments on invalid or even inadmissible evidence."

Read the indictment (App users go here)

A federal judge on Monday gave prosecutors a week to respond.

Three years after his grandfather's death, Carman allegedly became low on funds and lured his mother out for a fishing trip on a boat named the Chicken Pox, the indictment alleges.

Nathan Carman returns to shore

A US Coast Guard boat brings Nathan Carman to a Coast Guard base in Boston on Sept. 27, 2016, after surviving the sinking of his 32-foot fishing boat near Block Canyon, off New York, in the Atlantic Ocean on Sept. 18. He was picked up in a lifeboat about 100 nautical miles south of Martha's Vineyard on Sept. 25 by a Chinese freighter. His mother, who was on the "Chicken Pox" with him, has not been found.  (Suzanne Kreiter/The Boston Globe via Getty Images)

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The boat went missing, and days later, another vessel found Carman alone in an inflatable raft. Weeks later, he filed an insurance claim for $85,000 – which the insurer denied.