People who knew Aaron Traywick, the biohacker who died last month at a spa in Washington, D.C., were initially suspicious about the circumstances of his death.

David Ishee, a researcher for Mr. Traywick’s company, Ascendance Biomedical, said his first thought upon hearing that Mr. Traywick’s body had been discovered in a sensory deprivation tank was that he had faked it and run off with his clients’ money.

Tristan Roberts, another biohacker who worked with Ascendance, thought the same thing. Maybe the body was just “a very convincing clone,” he joked.

Kelly Martin, who helped found Ascendance Biomedical, had a different theory, one that hinted at a conspiracy. “There’s speculation, if you watch Aaron’s last video, that he was going to provide disruptive technology that would upend Big Pharma,” she said. “He said that we were close to coming up with something that was pretty revolutionary.”

The police do not suspect foul play and the cause of the death is unknown. Edwina Rogers, Mr. Traywick’s adoptive cousin, said a police detective told her that he found the drug ketamine in his pants pocket. She thought it likely that he had taken the drug, lost consciousness in the tank and drowned.

In the span of two years, Aaron Traywick, who was 28 when he died, went from a virtual unknown to a notorious personality in the biohacking community. At the time of his death, he was estranged from many of his closest collaborators.

He had remained close with his adoptive family, though they knew little about his work. His mother, Rita Traywick, was completely blindsided by the news. “He was fine, we saw him in April,” she said. “Talkative and proud of the work that he was doing.”

But Ms. Traywick, 70, said she barely understood his work. “He would tell us these things, and I would stand there and say, that’s great, we’re proud of you, and I couldn’t understand a thing he was saying to tell you the truth.”

Biohackers in general aim to augment their bodies in the hopes of gaining enhanced abilities. Those who work with the kinds of compounds that Mr. Traywick did often experiment on themselves so as not to break any of the laws that regulate health care.

Mr. Traywick’s company was founded in 2016 to provide funding, lab equipment and distribution to these D.I.Y. citizen-scientists. He seemed dedicated to investing in experimental compounds — formulas that would eventually be meant to treat diseases — that few others would touch.

Until several months ago, the company was viewed by many biohackers as a potentially groundbreaking venue for invention.

But Mr. Traywick proved to be secretive and aggressive. He kept the people he worked with away from one another, ensuring that he was the only person at his company with all the information. He tried to gain financial control over his collaborators’ inventions, and to sell them before they were fully tested.

Rich Lee, who created a vibrating penile implant called the Lovetron 9000, recalled that Mr. Traywick wanted to own 75 percent of profits made from sales of his device in exchange for funding. He said Mr. Traywick offered to pay him only $5,000 and was insistent that Mr. Lee presell the implant before it was finished and tested. “I was left with a bad taste in my mouth,” Mr. Lee said.

“He did seem to promise anything to everyone who was looking for something,” said Mr. Roberts, the Ascendance contractor. “He was actually developing some of the things he was saying he was developing. On the other hand, it did seem like he would take any money that people handed him with no regard for executing.”

By the time Mr. Traywick died, biohackers, researchers and engineers he had recruited had soured on his approach to the business.

Walt Crompton, an engineer and life extension enthusiast who worked as a contractor for Boston Scientific and other medical device manufacturers, started doing research for the company in the fall of 2016.

“I was allegedly a co-founder,” Mr. Crompton said. “At first there were big promises of equity sharing and so on but those things never materialized.”

Shortly after Mr. Traywick’s death, Mr. Crompton wrote an email to a friend about his ambivalence. He said that while the Ascendance founder’s behavior had convinced him to leave the company, he found himself “kicking the dirt, though, expecting that Aaron would go on to be rich and famous, while so many great contributors will not, precisely because of the way he elbows his way to the front of the line.”

Still, he wrote:

For me, it was enough that at least he was breaking through the frustrating inertia of our rejuvenation biotechnology movement. At age 65, and feeling the degenerative burn more and more, FDA timelines are just not good enough. Celebrating the heroism of "bio-hackers" comes easy. Funny, though, how his death has created a reactionary stir about bio-hacking, when, from all appearances, there was ZERO bio-hacking factors leading to his fall … Kinda like how a fringe anarchist assassinating the Archduke triggered WWI. Such is politics! We cannot expect logic and mercy to be primary forces in that realm.

Ascendance Biomedical was formed in the spring of 2016, not long before Mr. Traywick, then 26, was forced out of his adoptive cousin’s nonprofit, the Global Healthspan Policy Institute.

The cousin, Edwina Rogers, is a lobbyist and former economic adviser to the George W. Bush White House. She was also the founding executive director of the Secular Policy Institute, an organization that promotes the separation of religion and public policy, and is the chief executive of the Center for Prison Reform.

She did not know Mr. Traywick very well before she hired him. He had been adopted by her Aunt Rita and Uncle James so she would see him over the holidays, growing up.

But he gave her a call after he graduated from college to ask for career advice. She asked him what he was interested in, and one of the topics, life extension, was a passion she shared.

Ms. Rogers was interested in starting another organization dedicated to expanding healthy human lifetimes. So in January 2016, she founded the Global Healthspan Policy Institute and installed her cousin as the chief operating officer.

She also allowed him to move into the house she shared with her husband in Washington, D.C., a decision they would later regret.

Three weeks into his stay, Mr. Traywick told Mr. Neimeyer that after college, he had lived in a tantric sex house in Colorado and began to talk about his experience there. The discussion was disturbing, Mr. Neimeyer said.

“He had delusions that women wanted him,” Mr. Neimeyer said. “He’d be talking with them and promising them meetings with senators.” He said that at one point Mr. Traywick referred to the women he slept with as “my skanks.”

“He had a smooth-talking game, but beneath that thin veneer, he had a seething caldron of animosity and predation,” Mr. Neimeyer said.

The couple also began to realize that Mr. Traywick was lying to them. He intercepted professional correspondence that was meant for Ms. Rogers, and at least once, accepted an airplane ticket and a conference invitation on her behalf. One night in late March, when Mr. Neimeyer was out of town, Mr. Traywick attempted to force his way into Ms. Rogers’s bedroom at 2 in the morning.

Shortly thereafter, the family moved him into a new apartment.

“We were so desperate that we went and rented a place for him,” Ms. Rogers said. They told him: “This is your new home. You’re not welcome in ours.”

Several months later, Ms. Rogers terminated Mr. Traywick’s employment. “You have moved aggressively, unprofessionally, and incorrigibly against the directives that we have been giving you, demonstrating vividly your commitment to insubordination and unmanageability,” she wrote to him in an email on July 17, 2016.

“Aaron promised that he would work very hard and be a serious understudy,” she said. “He talked about a variety of experience he had but it was all smoke and mirrors.”

Mr. Traywick continued to tell people he was employed at the nonprofit for another year.

One of the ways Mr. Traywick convinced people to work with him — or to buy what he was selling — was the persona he affected. He used his brief experience working for his cousin to represent himself as a moneyed veteran of Capitol Hill, knowledgeable about health care policy and the structural limitations placed on researchers by the Food and Drug Administration.

He had already contacted dozens if not hundreds of people to talk about experimental ways to improve the human body. A group of individuals began to coalesce around him. Among them were a Dutch futurist named Demian Zivkovic, a British geneticist named Matt Johnstone, and a marketer from Oshkosh, Wis., Kelly Martin.

Ms. Martin, 39, said she began to speak to Mr. Traywick online between late 2015 and early 2016. She saw her new contact as a radical thinker on the order of Steve Jobs. “His ideas were kind of revolutionary,” she said.

Mr. Traywick encouraged this view of himself. In interviews and public appearances, he compared himself to Jonas Salk or Louis Pasteur, bold experimenters who pioneered lifesaving technology. Through Ascendance, he helped bring an experimental fertility treatment called Inovium to the United States. (Ms. Martin estimated that Ascendance had between 40 and 50 clients to whom it was selling infertility drugs. She said she did not know how much they were paying.) Mr. Traywick also sponsored an experimental gene therapy meant to treat H.I.V. that was also being tested by the National Institutes of Health. Mr. Roberts, his collaborator, eventually took that treatment.

Gennady Stolyarov II, the chairman of the United States Transhumanist Party, a political organization with close to 880 members that supports life extension through science and technology, had been corresponding with Mr. Traywick since November 2015.

“He definitely shared a lot of our values,” Mr. Stolyarov said. “I think Mr. Traywick was sincere about what he was doing. I don’t think he was trying to scam anyone or mislead anyone.”

In October 2017, Mr. Traywick hit the mainstream press for the first time and Mr. Roberts became Ascendance Biomedical’s first public guinea pig.

Sitting on a couch next to Mr. Traywick and another hacker, Mr. Roberts, who was diagnosed with H.I.V. in 2010, injected himself with an experimental gene therapy that was meant to treat the disease. They were filmed by an independent journalist, Ford Fischer, who broadcast the injection on Facebook Live.

Josiah Zayner, a prominent biohacker who that month had injected himself with modified DNA in an effort to enlarge his muscles, happened to be surfing Facebook at the moment that the live stream began. He was impressed.

“At the time no one was doing this stuff except me and one or two other people out on the fringes,” Mr. Zayner said.

“I think they were excited to be presenting the concept almost as much as they were to see the results from it,” Mr. Fischer, the documentarian, said. “Aaron had some really large notions of what could be done with this stuff in the future. He felt like this was the first step in being able to change the world.”

The injection prompted media attention. And it caused a stir within the biohacking community.

“I remember I just started contacting all these people I knew,” Mr. Zayner said. “Telling them you’ve got to check this out. After that it was kind of disappointing. Tristan, his viral load went up instead of going down. The treatment didn’t really work.”

Accredited scientists were also skeptical. Mark Connors, who led the team that discovered the antibody Mr. Roberts had injected, told the BBC: “These seem like very smart young men and they have command of some of the facts, but not all the facts.”

With the October injection, Mr. Traywick gained a measure of fame. He wanted to keep the momentum going so, several months later, he planned another stunt. This time no one, including his closest collaborators, knew exactly what he had in mind.

He reached out to the organizers of BDYHAX, a three-day body hacking conference to be held in Austin in February. He told them he wanted to do a live test of what he billed as an experimental vaccine for herpes. But the injection he had planned to take was not ready in time.

On Feb. 4, Mr. Traywick took the stage at the convention and told the audience that Ascendance Biomedical had developed a vaccine to cure herpes. He also announced that the company’s technology could be used to address a panoply of genetic diseases. Interested people were told to simply get in touch with Ascendance.

He dismissed an audience question about whether the procedure had undergone formal ethical oversight (“no”), and announced to the room that he had been diagnosed with herpes five years prior. Then, he took off his pants and injected himself.

“Nobody knew what he injected,” Mr. Zayner said. “He was trying to market this thing as a cure for herpes. He’s trying to promote and sell what he calls a cure and he doesn’t even know what it is that he used.”

Mr. Zayner also said as much on Facebook.

“The idea that any scientist, biohacker or not, has created a cure for a disease with no testing and no data is more ridiculous than believing jet fuel melts steel beams,” he wrote. “Ascendance Bio are not legit in any measure.”

The stunt in Austin set off a mutiny. Tristan Roberts and the others who had been working as contractors for Ascendance in the lead-up to the October and February injections met in Jacksonville, Fla. There, they confronted Mr. Traywick for exaggerating Ascendance’s accomplishments and for not paying them what he had promised.

They were also frustrated to discover that he had invited several film crews to Jacksonville to witness Mr. Roberts take another round of experimental H.I.V. therapy. But Mr. Roberts knew the compound wasn’t ready, and wouldn’t inject it.

A confrontation unfolded between the collaborators, some of which was caught by a camera crew from Vice. Mr. Traywick seized the key to the Jacksonville laboratory and had the locks changed. Most of the team left Florida dispirited. Mr. Roberts said that he would not work with Aaron again after that. Mr. Traywick told a journalist at Gizmodo, Kristen V. Brown, who reported on the fight, that he had fired his collaborators. “I love those guys and I want us to move forward together, and they have made it very difficult,” he told her. The other biohackers told her they had quit.

A month later, Mr. Traywick filed suit in federal court. Acting as his own lawyer, he said that Mr. Zayner’s Facebook post and Ms. Brown’s article had profoundly impacted his personal and professional life and his business interests. He said they had caused him and his company to suffer significant harm, “including financial losses, damage to their reputation, humiliation, embarrassment, mental suffering, shame and emotional distress.”

“These damages are ongoing in nature and will continue to be suffered in the future,” the lawsuit said.

It was dismissed on April 23. Six days later, Mr. Traywick’s body was found.