He repeatedly posted on Reddit about his recovery and offered words of encouragement for people with similar conditions, telling them to push back against doctors who suggested they had to live with pain.

But notably absent from the posts are explicit concerns about corporate greed in the health insurance industry. Those appear to have surfaced only later: in a handwritten note found after Mangione was detained as a suspect in the killing of UnitedHealthcare CEO Brian Thompson.

That short document references “parasites” in the health care system and laments the power and profits of health insurers, according to law enforcement officials. During his first public words since his arrest in Pennsylvania, Mangione emerged from a patrol car shouting about an “insult to the intelligence of the American people” while sheriff’s deputies pushed him into a courthouse.

There’s no indication Mangione was ever insured by UnitedHealthcare, a senior New York City police official said in an interview Thursday with NBC New York.

The killing has nonetheless prompted widespread speculation about whether he had a bad personal experience with the health care system. But after his 2023 surgery, Mangione’s Reddit posts suggest he was overwhelmingly pleased with the outcome and finally relieved of chronic pain. He encouraged others not to be frightened by horror stories of surgeries gone bad. He also referenced a backpacking trip to Asia earlier this year.

The 26-year-old Ivy League graduate appears to have stopped posting on social media roughly six months ago, around the time he lost touch with loved ones.

Family and friends expressed shock at news of Mangione’s arrest, but little information has emerged about his recent mental and physical health.

Mangione’s Reddit posts reference a spinal condition called spondylolisthesis, which occurs when a fracture causes a vertebra to slip out of alignment. It can result in severe pain if the bone puts pressure on spinal nerves.

The condition, which can originate in childhood or from an injury, started negatively impacting Mangione’s life in recent years, according to his social media posts.

After earning his bachelor’s and master’s degrees from the University of Pennsylvania, he worked at the Santa Monica-based car-buying website TrueCar until 2023 and lived in Hawaii for some time starting in January 2022. During a six-month stay at Surfbreak, a “co-living” space in Honolulu, Mangione’s back pain worsened in part because of a surfing incident.

Josiah Ryan, a spokesperson for the owner and founder of Surfbreak, R.J. Martin, said Mangione had expressed growing concerns about the pain. In addition to missing out on recreational activities and exercise, he was worried about how it could affect romantic relationships.

“That was definitely a theme in his time there,” Ryan said. “He wasn’t a big complainer. So it wasn’t like he was bringing it up constantly. But the people who knew him knew this was a significant part of his life.”

In July 2023, Mangione wrote in a Reddit post that he had decided to get surgery.

“I got caught in this loop for a year, all the while putting my life on hold in my 20’s and damaging my nerves while I waffled on the decision. I have surgery scheduled in two weeks and I keep wondering why I was so afraid of it,” he wrote.

According to his posts, the operation was a success.

An image posted to an X account linked to Mangione showed what appeared to be an X-ray of a metal rod and multiple screws inserted into his lower spine.

“Surgery was painful for the first couple days, but I was shocked that by day 7 I was on literally zero pain meds,” Mangione posted on Reddit in August 2023. “Obviously will be awhile until I get into rigorous activity, but it was way less of a big deal than I had anticipated.”

Medical experts say treating back pain is almost always a challenge.

“In the gross majority of treatments, surgery is when everything else has failed to provide relief,” said Dr. Jason Pittman, co-director of the Spine Center at Boston’s Beth Israel Deaconess Medical Center. He said doctors generally try conservative treatments like physical therapy, injections or medications before surgery.

Even people with health insurance can face thousands of dollars in bills from a surgery depending on their deductible and other factors, though it’s unclear whether Mangione experienced any of those issues.

Experiencing chronic back pain can also significantly impact mental health, said Dr. Padma Gulur, a pain specialist with Duke Health.

“If you have underlying mental health issues — anxiety, depression — your pain can be worse because you have way more suffering,” Gulur said. “But, the second aspect is pain can push you into anxiety and depression.”

Little is known about Mangione’s mental state in recent months, but it appears he was withdrawing from close relationships. Since-deleted posts on X show a friend repeatedly reaching out and getting no response.

His family reported him missing to San Francisco authorities in November, police said.

Earlier, while in college, Mangione posted on Reddit about experiencing severe brain fog and restless sleep.

In a July 2018 post, he said his grades were suffering and he had considered dropping out of school. But ultimately, “staying in college has at least let me maintain some semblance of normality,” he wrote.

His last Reddit post is dated May 17, but other statements around that time suggest he wasn’t experiencing unexpected complications or renewed back pain. He appears to be advocating for the type of surgery he received months earlier.

He posted in early April about the gear he brought on a two-month backpacking trip through Asia that included some cross-country motorcycling, saying he had found “the perfect balance between minimalism and practicality.”

In late April, he advised another Reddit user with a back problem to “keep trying different surgeons” and, if necessary, convey an inability to keep 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.”