Nathan Carman and his mother, Linda, embarked on a fishing trip late one September night in 2016, setting sail from a Rhode Island marina.

They were headed to waters near Block Island in Nathan’s 32-foot aluminum boat, named Chicken Pox, in search of tuna. Linda and her son bonded during overnight fishing trips like these, a friend said before Carman was rescued at sea.

The day after they set sail, according to Carman’s statements to the Coast Guard, he heard a “funny noise” in the engine and the boat capsized soon after. “I looked and saw a lot of water,” Carman said in a radio call with the agency after his rescue, adding, “The boat just dropped out from under my feet.”

“When I saw the life raft, I did not see my mom,” Carman continued. He said he grabbed an emergency kit with food and water and swam to the inflatable raft and whistled and called out for Linda. But she was nowhere to be seen.

Carman claims he was drifting for seven days when a passing Chinese freighter, the Lucky Orient, found him about 100 miles south of Martha’s Vineyard.

When Carman got to land, he didn’t receive the warm welcome he expected. “I was lost at sea, my mom died,” the now 24-year-old said in a 2017 interview with ABC’s 20/20. “What would be great, to have people embracing you saying we are glad you are home, we are glad you are alive and also helping me to deal with my mom's death. It hasn't been that.”

Now Carman is battling two separate lawsuits—from his boat's insurer and from his own family—alleging he caused his mother’s death by deliberately sinking his ship.

He’s also facing accusations that he allegedly murdered his wealthy grandfather, John Chakalos, about three years before the supposed boat accident.

Authorities immediately had questions about the mysterious shipwreck that presumably claimed Linda’s life, and police executed a search warrant on Carman’s rural Vermont home.

In an affidavit, a detective in South Kingstown, Rhode Island said police sought maps, GPS devices and computers, and other items that would provide information about the destination of the fishing excursion, as well as receipts for boat equipment.

“This investigation revealed that Nathan’s boat was in need of mechanical repair and that Nathan had been conducting a portion of these repairs upon his own volition which could have potentially rendered the boat unsafe for operation,” the affidavit stated.

Hubert Santos, Carman’s former attorney, told the Associated Press that Carman “fully cooperated” with the Coast Guard.

“It was a tragic accident,” Santos said, as a cloud of suspicion swirled around Carman.

Still, in 2013, Carman was the main suspect in another family death: the unsolved murder of the 87-year-old Chakalos. Carman was never charged or arrested in connection to the killing.

Carman’s father, Clark, told CBS Boston that Carman would never hurt his mother or grandfather. “They were the two most important people in his life,” Clark said in a September 2016 interview after Carman was rescued.

“He’s a good kid,” Clark added. “He loved his grandfather. It’s all being drudged [sic] up, and I really hate to see that, because there’s no substance to it.”

But lawyers for an insurance company—which is fighting Carman’s $85,000 claim for the Chicken Pox—claim Carman intentionally cut four half-dollar size holes in the vessel and made it “unseaworthy” before he and his mother sailed away.

And the attorneys have linked Chakalos’ fatal shooting to their boat lawsuit, filed in Rhode Island federal court.

“He instructed his mother to reel in the lines but he neither gave her a life vest nor told her the bilge was flooded,” lawyers David J. Farrell, Jr. and Sean T. O’Leary, who represent the insurer, wrote in court papers filed Dec. 28.

“Despite the boat’s open deck design, he never saw, spoke with, or heard from her again and as with his grandfather, Nathan Carman was the last person to see her alive,” stated in the filing on behalf of the plaintiffs, National Liability & Fire Insurance Company and the Boat Owners Association of the United States.

Police and the insurers aren’t alone in their suspicions that Carman could have been involved in the deaths of his maternal grandfather, who left behind a $44-million estate, and possibly his mother.

In 2017, Linda’s three sisters filed a lawsuit to stop Carman from inheriting millions of dollars from Chakalos’ and Linda Carman’s estates.

According to the Boston Globe, the complaint filed in probate court in Concord, New Hampshire requested that a judge declare Carman the murderer of Chakalos “and that Nathan committed this heinous act out of malice and greed.”

Dan Small, an attorney for the sisters, has previously said their legal action “is not about money, it is about justice.”

“The surviving sisters cannot stand idle while their father’s killer, and perhaps their sister’s killer also, profits from his actions,” Small said in a statement, after the lawsuit made headlines.

A trial in the probate case is scheduled for later this month. Small’s firm declined to comment when reached about the upcoming court date.

While Carman has attorneys in the Rhode Island matter, he appears slated to represent himself in New Hampshire.

Carman hung up on a Daily Beast reporter on Thursday when asked about the probate trial. In interviews over the years, he’s denied playing a role in the demise of his relatives.

“I have no idea who killed my grandfather. I know that I did not,” Carman told reporters outside one May 2018 court appearance, according to CBS Boston.

“I had nothing to do with my mother’s death. I did not do any of the things I’m accused of,” Carman continued. “It’s been extremely, extremely difficult for me these past couple of years.”

Indeed, Carman has claimed police targeted him because he has Asperger’s syndrome, a developmental disorder on the autism spectrum that can include difficulty with social interactions and unusual or monotone speech patterns.

“I think the police saw me as the lowest hanging fruit after my grandfather died because they saw that I had been diagnosed with Asperger’s,” Carman told ABC’s 20/20 in February 2017.

His former attorney, Hubert Santos, added, “There's an element here of prejudice against Nathan because of his disability, because when the police talked to him, they immediately become suspicious because of his odd manner.”

According to a New York magazine profile, Carman “displayed above-average intelligence, consistently earning high honors in high school. But those who knew him said he had the social aptitude of a child.”

Carman was described as a loner who was bullied in school. One fellow student told the magazine that Carman “was very insistent that he was right” and “would knock stuff over or whatever off the desk” during classroom debates.

“He was very passionate about the Second Amendment,” another classmate told New York. “He believed U.S. citizens should be allowed to buy any form of weapons, including rocket launchers, automatic weapons, grenades.”

Carman and his mother had a rocky relationship, and Linda and her father sometimes fought over Carman’s medical treatment. “Linda felt her father was butting into what she was trying to do with Nathan,” Clark told New York. “So there was some resentment.”

In May 2011, Linda was arrested for assault on an elderly person following an argument with Chakalos in a psychiatric hospital where Carman was admitted, but Chakalos asked that the charges be dropped, WCVB in Boston reported.

Linda would tell police, “My father is worth $300 million and I want my share. He’s not going to cut me off. I need money.”

Months later, a 17-year-old Carman ran away from home, distraught over the death of his horse named Cruise. He was discovered in Sussex County, Virginia, days later with two framed photos of himself with the animal, along with $4,000 in cash. He was planning on heading to Florida, he told the sheriff’s deputy that found him.

“I don’t know what his final plan was, he’s so typically level-headed,” Linda Carman told the Courant in 2011. "The only thing we can think of is that he’s big into fishing, and there’s horses in Ocala, so Florida has both of those things."

Two years later, Linda and her son would be on cops’ radar again when Chakalos was shot dead in his Windsor, Connecticut home on Dec. 20, 2013. Police announced they were investigating the philanthropist's death as a homicide.

A millionaire real-estate developer, Chakalos was known for a massive, 6-million-light Christmas display at his property in New Hampshire that helped to amass donations for a local food pantry. He died of a gunshot wound to the head, the medical examiner ruled.

His wife, Rita, died of cancer the month before, relatives said. For decades, the couple split their time between homes in Connecticut and New Hampshire. “John dedicated his life to his marriage, work and community, and above all, family,” Chakalos’ obituary read. “His favorite motto was ‘without family you’ve got nothing; family is everything.’”

According to the Hartford Courant, Windsor police were ready to arrest Carman for his grandfather's shooting in July 2014, when they submitted an arrest warrant for murder, but prosecutors wouldn’t sign off on it. At the time, Carman was living in an apartment in Middletown, Connecticut.

Prosecutors returned the warrant with a “request for further information,” and Carman was never charged, the Courant reported.

A 2014 warrant to search Carman’s apartment alleged Carman had dinner with Chakalos just before he died and was the last known person to see him alive. The next morning, one of Chakalos’ daughters found him dead, with three bullets in his head and torso.

Investigators pegged Carman as a suspect after interviewing Linda, who told cops that her son was supposed to meet her at 3 a.m. so they could drive to Rhode Island but he never showed up, the search warrant states.

“I was late in meeting my mom as I frequently was,” Carman told the AP. “I’m not always the person who is on time.”

Police later discovered Carman had purchased a Sig Sauer semiautomatic rifle in New Hampshire that was the same caliber as the firearm used to kill Chakalos, the probate lawsuit states. Carman declined to take a polygraph test and hid the purchase of the assault weapon—which is now missing—from investigators, the aunts claimed.

In written answers to questions posed by the aunts’ lawyers, Carman said he refused the lie detector “because the accuracy and reliability of polygraph results are questionable, and the principle of attempting to prove my innocence, a seeming waiver of one of the most fundamental human rights, the right to be presumed innocent until proven guilty, is abhorrent to me.” (Carman’s aunts and his mother, Linda, took and passed polygraph tests after Chakalos died, their lawyers have said.)

Meanwhile, according to the latest court filing in the insurance lawsuit, Carman bought the rifle for $2,099 on Nov. 11, 2013, while his grandmother Rita was in hospice.

Carman “and the Sig Sauer were criminally involved” in Chakalos’ murder in December 2013, the Dec. 28 court document claims, adding that the weapon “was capable of firing the same caliber rounds which killed his grandfather.”

“In the morning Nathan Carman went fishing on a head boat out of Point Judith, RI, jettisoning his Sig Sauer rifle which now lies at the bottom of the sea,” attorneys for the insurance firm added.

Carman is also accused of destroying his laptop’s hard drive and his truck’s GPS, and of obtaining access to roughly $587,000 after Chakalos’ death.

“Lacking gainful employment or educational pursuit, Nathan Carman then engaged in a similar scheme with chilling parallels. Using part of those monies, in December 2015 at the age of 21 he purchased a 31-foot diesel boat for $48,000. He insured it with Plaintiffs under the terms of the Policy, first registering it in New Hampshire. Upgrading the boat, he increased its insured value to $85,000 on March 25, 2016,” the lawyers said.

When the boat sank, its electronic navigational equipment also vanished, “just like Nathan Carman’s Sig Sauer rifle and his truck’s GPS after his grandfather’s murder,” the insurance company’s attorneys allege.

In October 2018, Carman was ordered to bring his Sig Sauer .308-caliber rifle to a secret deposition conducted by the insurer’s attorneys. (He did not produce the weapon, the company’s lawyers say.)

Shortly after, Carman’s lawyer, David F. Anderson, filed documents claiming his grandfather’s alleged mistress was linked to the murder. The court filing sought permission to depose the woman, identified as “Mistress Y,” as part of the insurance case.

Anderson wrote that “in comparison to the evidence supporting Plaintiffs’ murder claims against Mr. Carman, the evidence that ‘Mistress Y’ was involved with Chakalos’ murder, is far stronger.”

“Similarly, testimony from ‘Mistress Y’ is likely to establish facts from which one could reasonably conclude that Mr. Chakalos’ lifestyle and activities prior to his death made him a target of robbery and/or murder by some unknown person(s),” Anderson continued.

At the time of Chakalos’ murder, Mistress Y was a beautiful 25-year-old woman who’d met the developer earlier in 2013 while working at one of his housing complexes in New Hampshire, Anderson alleged.

The court filing claims Chakalos handed the woman up to $800 every time he took her out to lunch or visited her. By August 2013, their relationship allegedly involved Chakalos giving her cash in exchange for sexual favors.

The weekend before he died, Chakalos treated Mistress Y to a trip to Connecticut's Mohegan Sun Casino where they shared a bed and he gave her at least $3,500, court papers allege.

On Dec. 19, 2013, Carman and Chakalos dined at a local restaurant, and Carman drove his grandfather home around 8:30 p.m., the filing states.

“If deposed, testimony from ‘Mistress Y’ will establish that she called John Chakalos at his home at 8:36 pm in the evening,” the document continues. After answering the call, Chakalos allegedly told the woman that Carman was leaving and asked her for a minute “to say goodbye to my grandson,” court papers state.

Mistress Y and Chakalos spoke on the phone for 20 minutes that night. The woman “had knowledge that John Chakalos was worth millions, that he was 87 years old, hard of hearing, that he always had large amounts of cash and from her conversation with Mr. Chakalos that evening, she knew that he was going to be home all alone the entire night,” Carman’s lawyers wrote in the document.

Dan Small, the lawyer for Carman’s aunts, called the filing a “shameful attack” on Chakalos.

“Nathan’s shameful attack on his grandfather today shows there is no depth to which he will not sink to avoid producing his gun, which is the probable murder weapon,” Small said in a statement last year, according to the Courant.

“Now he is trying to cast blame on his own aunt, even though she willingly took and passed a police lie detector test, while Nathan refused, and she cooperated fully and honestly with the police, while Nathan lied repeatedly, including about this very gun.”