U.S. Attorney Nikolas Kerest of the District of Vermont arrested Carman, 28, on Tuesday. A federal indictment accused Carman of murdering his mother, Linda Carman, and sinking their boat "during a supposed fishing trip off the coast of Rhode Island" on Sept. 18, 2016, in an effort to obtain millions of dollars of inheritance and insurance money.
Rescuers discovered Carman on a life raft about 100 nautical miles south of Martha's Vineyard on Sept. 25, 2016.
The indictment also accuses Carman of shooting and killing his grandfather, John Chakalos, at Chakalos’s home in Windsor, Connecticut, in 2013 — also in an apparent effort to obtain family money and property.
Kerest on Wednesday also filed a motion to detain Carman ahead of his trial due to a flight risk, claiming the 28-year-old "poses a danger to the community" if he is not detained.
As part of Carman's alleged "scheme" to kill his mother and grandfather in exchange for his inheritance, "Carman concocted cover stories to conceal his involvement in those killings," the motion for Carman's detention states.
"During the cover-up, Carman misrepresented his involvement in and responsibility for those deaths to law enforcement, to his family, to those who made inquiries about the deaths and their circumstances, and to others who challenged his cover-up or challenged his rights to his grandfather’s assets," the document reads.
The filing also claims Carman received mental health treatment as a minor but stopped as an adult.
"His conduct severed his ties with his remaining family. He lives alone, has no children or significant other, and has been unemployed for years," the motion states. "Additionally, Carman was treated for mental health issues from the time he was a small child until he was  years old. Since that time, Carman has avoided any mental health treatment. Collectively, these factors create a powerful incentive for Carman to flee, which can only be mitigated by his pre-trial detention."
Motions in the case must be filed by Aug. 12, at the request of the defense, according to a criminal pretrial order filed Wednesday.
At the time of his mother's death, Carman claimed the pair had set off from a Rhode Island marina on their fishing boat, named the Chicken Pox, about a week earlier when the 31-foot vessel began gaining water near Block Canyon, off Montauk Point, New York, in the Atlantic Ocean. He claimed his mother mysteriously vanished while he hastily swam for the life raft.
The U.S. Coast Guard transported Carman back to their base in Boston, Massachusetts. His mother is presumed dead, though her body has never been recovered. Federal prosecutors now allege Carman purposely sank the boat, and witnesses have testified that he made faulty repairs before the voyage, removing two stabilizing trim tabs from the stern, near the vessel’s waterline, leaving holes that he tried to seal with an epoxy stick.
In 2019, U.S. District Judge John McConnell denied an $85,000 payout on Carman’s insurance claim on the sunken vessel.
If convicted of murder, Carman faces life in prison.
Fox News' Danielle Wallace and The Associated Press contributed to this report.