NEW YORK, United States — A US man was charged Tuesday with killing his mother at sea in a bid to inherit his family’s estate.

Prosecutors say 28-year-old Nathan Carman, from Vermont, murdered Linda Carman and sank their boat during a supposed fishing trip off Rhode Island in the northeast of the country in 2016.

He was arrested on Tuesday and charged in an eight-count indictment, the US Justice Department said in a statement.

Carman also shot and killed his grandfather John Chakalos at the latter’s home in Windsor, Connecticut in 2013, according to a separate, older indictment, prosecutors said.

The new indictment alleges that Carman murdered his two relatives as part of a scheme to obtain money and property from the estate of Chakalos and related family trusts.

Prosecutors also accuse Carman of attempting to defraud the company that insured his fishing boat.

Carman was found alone in an inflatable raft eight days after he went fishing with his mother, according to US media reports. Her body has never been found.

Carman is due to be arraigned in court in Vermont on Wednesday.

He faces mandatory life imprisonment if convicted of murder. The fraud charges each carry a potential penalty of up to 30 years in jail.