PROVIDENCE, R.I. (AP) — An insurance company investigating the sinking of Nathan Carman’s boat in 2016 is suggesting that he may have thrown a gun used to kill his grandfather into the ocean.

National Liability & Fire Insurance Company and the Boat Owners Association of the United States sued Nathan Carman in federal court in Rhode Island. They’re investigating his claim for his boat, which sank during a 2016 trip he took with his mother. She disappeared.

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Nathan Carman arrives at the Coast Guard base in Boston, Sept. 27, 2016. (WBZ-TV)

The Boston Globe reports the company said in a filing Carman and the rifle were “criminally involved” in his grandfather’s 2013 murder in Connecticut, and the weapon “lies at the bottom of the sea.”

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A message seeking comment was sent to Carman’s lawyers Monday.

Carman denies involvement in the deaths of his grandfather and mother. No one’s been charged.

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