Son Told Rescuers His Mom Was 'Likely' Dead After She Vanished on Their Fishing Trip

In a pair of letters to the captain of the freighter that saved his life, Nathan Carman wrote about losing his mother, PEOPLE confirms

In a pair of letters to the captain of the freighter that saved his life after days at sea, Nathan Carman wrote that if his mother is lost, he will be “alone in the world,” PEOPLE confirms.

“If my mom is lost, which I fear is likely, I will have no one on Earth who will welcome me sincerely into their home,” Carman wrote to Capt. Zhao Hengdong of the Orient Lucky soon after he was rescued, according to the Hartford Courant.

Tom O’Reilly, a port agent who worked with Hengdong’s crew, confirmed the authenticity and contents of the letters to PEOPLE, noting that Carman wrote that he “expects his mother has not survived” and was “quite despondent.”

Carman, 22, and his 54-year-old mother, Linda, went missing on Sept. 18 after they left Rhode Island to go on a fishing trip in a boat called “Chicken Pox,” the Courant reports.

Carman was found a week later off the coast of Martha’s Vineyard, Massachusetts, drifting on a life raft in good condition. But his mother — who was never found — is presumed dead. Carman told authorities their 32-foot aluminum fishing boat sank after apparently experiencing some kind of mechanical failure.

He has come under scrutiny since the rescue. Though Carman has not been charged with any crime, authorities are investigating him for reckless endangerment in connection with his mother’s disappearance, ABC News reported.

Police suspect he took his mother out on the boat even though it needed mechanical repairs.

“I know I wasn’t responsible for the boat sinking,” he told ABC News. “I know that I wasn’t responsible for anything that resulted from the boat sinking. I know I wasn’t responsible for my mom’s death.”

PEOPLE has not been able to reach Carman for comment.

Michael Dwyer/AP

The crew found Carman floating on a life raft in the Atlantic Ocean and rescued him on Sept. 25, O’Reilly says.

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He tells PEOPLE that, according to the captain, Carman stayed in his room resting his first day on the freighter, but when he emerged from his room the next day he kept asking if anyone had found his mother.

“[Hengdong] said Nathan did come out … and he again asked if there was any sign of his mother. He was told there was not, and the captain said he really was quite despondent about the fact that he had lost his mother in this accident,” O’Reilly says.

“He said for the whole two days there was no smiling or any kind of thing like that from Nathan … He said he did appear to be very sad about what happened,” O’Reilly says. “[Carman] wrote his thoughts down in a letter and gave it to the captain.”

In the letter, Carman told the captain that if he ever visited America he would love to show him around, according to the Courant and O’Reilly.

O’Reilly says Carman even wrote his “philosophical thinkings” about God, telling the captain that he trusted that God would look after him while he was lost at sea.

Reports have also surfaced that Carman was once a suspect in the unsolved 2013 slaying of his grandfather John Chakalos, after which Chakalos’ multimillion-dollar estate was left to his children, including Carman’s mother.

Carman has said that he had nothing to do with the man’s death.