After a hike through one of Japan’s lush mountain ranges this year, Luigi Mangione, a computer engineer in his mid-20s who had set off on a long solo trip to Asia, paused to record a voice message to a friend.

Making his way that day along a river gorge in the Nara region, Mangione had fled his day-to-day life in Hawaii to soak in hot springs, meditate, catch up on books and do some writing.

“I want some time to Zen out,” Mangione said in the recorded message on April 27.

It would be one of his last communications before he abruptly cut ties with a wide range of friends and family, who eventually set out on a desperate hunt to track him down. Seven months later, Mangione emerged from his isolation as the suspect in the brazen assassination of Brian Thompson, chief executive of UnitedHealthcare, on a sidewalk in Manhattan.

Police investigators have been scrambling to trace Mangione’s movements not only in the days before the December 4 shooting, but also in months that preceded it.

Friends and family members have been left bewildered by the jarring transformation of a young man who had seemed destined for a life of achievement. He was the valedictorian at his elite prep school in Maryland and a computer science graduate of the University of Pennsylvania’s acclaimed engineering program.

But his writings and messages also traced a darker journey in “unbearable pain”.

He expressed alarm over the world’s increasing reliance on smartphones and social media. During his trip to Asia, he lashed out at the “modern Japanese urban environment”, claiming that a lack of “natural human interaction” was responsible for falling birthrates and a dearth of human connection.

More and more, he expressed frustration that society seemed incapable of addressing these problems, and he expressed interest in those who said that violence might be a necessary next step.

In his possession at the time of his arrest in Altoona, Pennsylvania, police said, were writings that condemned a multibillion-dollar health care industry that he said had put profits ahead of extending lives: “Frankly, these parasites simply had it coming.”

Mangione is charged with second-degree murder in the death of Thompson. His defence lawyer, Thomas Dickey, said his client was presumed innocent and urged the public to keep an open mind.

Mangione’s medical struggles seemed to escalate during his studies at the University of Pennsylvania. Underneath Mangione’s friendly, accomplished exterior, he was struggling to adapt to college.

He wrote on social media that his fraternity’s “hell week”, despite being “very tame”, had disturbed his sleep cycle and drastically worsened symptoms of “brain fog” that he had been experiencing since high school. Once a straight-A student, Mangione wrote in a series of since-removed posts on Reddit that he suddenly saw his grades slipping.

“It’s absolutely brutal to have such a life-halting issue, especially since the issue itself wears down the critical/logical thinking mind you’d usually use to tackle it,” he wrote. “The people around you probably won’t understand your symptoms – they certainly don’t for me.”

Among those who struggled to understand his ailments were his doctors; he suggested that tests that might explain his symptoms kept coming back negative.

Mangione did his own hunting for answers. He talked about getting Lyme disease at age 13 and seeking out new tests as an adult. Some studies have found that effects of the disease, including fatigue, brain fog, pain, sleep disruption and tingling or numbness in parts of the body, can linger long after treatment.

Mangione also consulted others online about irritable bowel syndrome and visual snow, a neurological condition in which a person’s vision is obscured by flickering dots. While he appears to have sought doctors’ help for his brain fog symptoms, he did not mention being treated for mental illness.

Despite his struggles, Mangione continued to show academic brilliance and an entrepreneurial spirit. In the summer of 2019, he was chosen to be the head counsellor of a precollege program at Stanford University in California. When he returned to Penn for the school year, one fellow student recalled, he was ready to make some money. He bought dozens of boxes of Christmas lights and stacked them in a stairwell at his off-campus apartment, selling them to students to decorate their residences around campus.

As the pandemic arrived during his senior year in 2020, Mangione completed both a bachelor’s degree and a master’s degree simultaneously. He soon secured a job at a California-based tech company.

Able to work remotely, Mangione moved in early 2022 to Honolulu, settling into a co-living space in a high-rise near Waikiki, Hawaii. But soon after, his medical troubles worsened following a group surfing lesson, and he complained that he had strained his back.

“His spine was kind of misaligned,” said R J Martin, who had founded the co-living space and grew to be friends with Mangione. “He said his lower vertebrae were almost like a half-inch off, and I think it pinched a nerve. Sometimes he’d be doing well and other times not.”

It hurt to sit down, he reported, and his leg muscles were twitching. He felt tingling and numbness in his groin.

For months, the suffering continued as he consulted doctors and tried various noninvasive remedies. He quit his job in early 2023, telling a friend that it was “mind-numbingly boring”. He said he wanted to spend more time doing yoga and reading.

It is not clear how he paid for health care after that. In May, he turned 26, meaning that he could have been kicked off his parents’ health insurance plan. The family has declined requests for interviews.

Mangione had always been a voracious reader, scribbling extensive notes that would summarise the author’s views and how they might apply to his own life. “Reflect on how current work can positively impact society,” he wrote while reading Grit: The Power of Passion and Perseverance, a book about how to overcome setbacks by intentionally cultivating tenacity.

Among friends in Hawaii, he helped start a book club that began meeting in 2023. Mangione pushed for readings by Tim Urban, a writer-illustrator whose blog “Wait, But Why”, is popular with Gen Z techies. The group also read The Ape that Understood the Universe”, a favourite of Mangione’s that explores evolutionary psychology.

One focus of his reading was his ongoing back troubles, including Crooked: Outwitting the Back Pain Industry and Getting on the Road to Recovery. In the summer of 2023, he decided it was time to pursue surgery, travelling back to the east coast for the procedure. On August 10, Martin texted him to ask how it had gone, and Mangione texted back a laughing emoji and photos of his spinal X-rays.

He reported on Reddit that the procedure was a success and that he could walk and sit just fine within days. He began encouraging others to consider surgery and to push back against doctors who might be wary of surgical solutions. He suggested at one point that people should perhaps tell their doctor that their back troubles were preventing them from working.

“We live in a capitalist society,” he wrote. “I’ve found that the medical industry responds to these key words far more urgently than you describing unbearable pain and how it’s impacting your quality of life.”

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Among his friends in Hawaii, there was a growing strain among members of his book group, participants said. Some of them were perturbed by Mangione’s book selections, which they felt were overly geared toward masculine pursuits. Others drifted away after a discussion about whether to read the writings of Ted Kaczynski, the so-called Unabomber.

Martin said he was the one who proposed reading Kaczynski’s manifesto, but Mangione was also clearly a fan, praising it later on his Goodreads page. Mangione quoted what he described as “interesting” remarks from someone who had written about how companies “have zero qualms about burning down the planet for a buck, so why should we have any qualms about burning them down to survive?”

The passage went on. “How long until we recognise that violence against those who lead us to such destruction is justified as self-defence?”

After his surgery, Mangione toured the islands of Hawaii, visited family in Maryland and this year set off on the trip to Asia, which included stops in Thailand and Japan.

He wrote that he found Japan’s densely urban environment to be “an evolutionary mismatch for the human animal”. But he loved the mountains, saying that one of his goals in Asia was to “do some Buddha”.

He described his travels in Nara with enthusiasm. “There’s like these tiny little villages here, on the side of the cliffs — I’ll send a photo. It’s super lush, there’s this beautiful river that cuts through the gorge,” he said in the voice message he left in April. “I think I want to stay here for like a month, and just meditate and just hot spring, and do some writing.”

Mangione sent another message to the friend he had met while travelling. He was on Mount Omine in Japan, which he noted was known for its tests of courage and also for prohibiting women from climbing it. “This mountain is peak misogyny,” he wrote to the friend. But, he added, “I needed to stop getting distracted by women lol.”

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On May 25, Mangione’s Reddit account shows one final post, on a subreddit dedicated to Kaczynski.

Not long after that, friends started to lose touch with Mangione. One texted him in June – “Where in the world are you?” – but received no reply. By the end of the summer, family members were reaching out to Mangione’s past friends, hoping for their help in tracking him down.

His relatives have not discussed why they waited until November 18 to file a missing person’s report in California.

Just a few days later, police say, Mangione got on a bus, on his way to New York City.

This article originally appeared in The New York Times.