BRATTLEBOROUGH, Vt. (WTNH/ABC) — A still developing story about a mystery at sea. Investigators are trying to figure out whether Nathan Carman had anything to do with his mother’s disappearance. The two disappeared more than a week ago before a freighter found him alive. But his mother is still missing.

Nathan Carman was the last one to see his mother, Linda, alive. Carman answered questions for ABC News about his 8 days lost at sea, saying he wouldn’t have brought his mother out fishing if knew there was a problem with their boat.

I would not have brought my mom out finishing with me had I thought the boat wasn’t sea worthy. She’d always had been reluctant about safety and I guess she had good reason to be.”

Police are trying to find out more about the 22-year-old Middletown native who was rescued, but his mother wasn’t. A search warrant revealed that Carman is under investigation for reckless endangerment, “resulting in death.”Related: News 8 Legal Expert speaks on Nathan Carman case

His boat, it says, was in need of mechanical repair and that Carman could have potentially “rendered his boat unsafe for operation.” Carman, who has Asperger’s syndrome, says he lost sight of his mother as he scrambled into a life boat.

I didn’t think we were sinking. I didn’t know we were sinking until we sank,” said Carman. “I did see the life raft. I did not see or hear my mom. I was calling out to my mom.”

Related: Search warrant issued on Vermont home of Middletown native rescued after ordeal at sea

Carman says he’s devastated to have lost his mother but knows she would have wanted him to survive. Detectives issued a search warrant at his home in Vermont but this isn’t the first time he’s been a suspect. Days after his grandfather was murdered in Windsor in 2013, he was the last person to see his grandfather alive.

And the search warrant obtained by News 8 it says Carman had a fascination with firearms. Police issued a search warrant on Carman’s home. He removed hard drives and sim cards from his electronic devices the day his grandfather’s body was found. No arrest was made but a reward has been offered for this ongoing cold case. All of it circumstantial evidence according to News 8’s legal analyst, Tara Knight.Related: Report: Man rescued at sea was suspect in grandfather’s killing

“We don’t have any other witnesses; we don’t have any video tape, we don’t have any DNA, we don’t have a confession. So it is suspicious circumstances that are making a building block that could eventually lead to an arrest,” said Knight.

It’s estimated the grandfather was worth just under $50 million.