A 28-year-old man who was rescued from a raft off the coast of New England in 2016 after his boat sank pleaded not guilty Wednesday to charges he killed his mother at sea to inherit the family’s estate.

Nathan Carman was arraigned in federal court in Rutland on multiple fraud charges and a first-degree murder charge in the death of Linda Carman. He shouted “not guilty” in the direction of reporters who had asked him on his way into the courthouse whether he killed his mother.

Authorities allege in the indictment unsealed Tuesday that Carman also killed his grandfather, John Chakalos, at his home in Windsor, Connecticut, in 2013 as part of a scheme to obtain money and property from his grandfather’s estate, but he was not charged with that killing.

“As a central part of the scheme, Nathan Carman murdered John Chakalos and Linda Carman,” the indictment reads.

Carman was found in an inflatable raft eight days after leaving a Rhode Island marina to go fishing with his mother, who was never found. Prosecutors allege Carman altered the boat to make it more likely to sink that day. He has denied doing anything to intentionally make the boat unseaworthy.

Carman, who was arrested Tuesday, faces life in prison if convicted of killing his mother, Linda Carman, of Middletown, Connecticut. His attorney did not comment after the arraignment.