The prime suspect in the killing of UnitedHealthcare’s chief executive, Brian Thompson, Luigi Mangione, may have fallen into a spiral of despair after having back surgery for a chronic condition — recently cutting himself off from family and friends.

The motive for the shooting is still not clear, but new details have emerged since he was arrested on Monday and charged with murder. The 26-year-old reportedly suffered from the debilitating effects of a spinal condition that may have affected his mental well-being as well.

In late 2023, Mr. Mangione had undergone surgery to treat his Spondylolisthesis. This condition causes vertebrae to shift forward onto the vertebrae below, causing “significant pain” and “nerve injury,” according to the American Academy of Orthopaedic Surgeons. In the months after, he became increasingly isolated, cutting off all contact with his family and loved ones.

“I don’t know if you are okay or just in a super isolated place and have no service. But I haven’t heard from you in months,” one person posted on his X account in July.

Mr. Mangione’s mother had reported him missing and had reached out to friends in an attempt to locate him, according to a report by the New York Post. 

From January to June 2022, Mr. Mangione lived at Surfbreak, a “co-living” space at the edge of Honolulu tourist mecca Waikiki.

Like other residents of the shared penthouse catering to remote workers, Mr. Mangione underwent a background check, said a spokesman for owner and founder R.J. Martin, Josiah Ryan.

At Surfbreak, Mr. Martin learned Mr. Mangione had severe back pain from childhood that interfered with many aspects of his life, from surfing to romance.

“It was really traumatic and difficult, you know, when you’re in your early 20s and you can’t, you know, do some basic things,” Mr. Martin said to CNN, adding that after a surf lesson, Mr. Mangione had ended up “in bed for about a week” with back pain.

While at Surfbreak, Mr. Mangione helped lead a book club and enjoyed hikes and yoga. While the residents discussed topics like capitalism and health care, Mr. Mangione never gave any indication that he was planning a violent act.

“It wasn’t like he had an ax to grind, or he was even upset or angry about a particular issue,” he said.

Mr. Martin stopped hearing from Mr. Mangione six months to a year ago.

A Goodreads account maintained by Mr. Mangione showed more than 250 books read and a list that spans everything from politics to health. He gave a four-star review to the Unabomber Manifesto of Ted Kaczynski.

He referred to Kaczynski as a “violent individual” and that he was “rightfully imprisoned” but that his actions were, “those of an extreme political revolutionary.”

On Monday, Mr. Mangione was arrested at Altoona, Pennsylvania, after the McDonald’s customer recognized him and notified an employee, authorities said. Police in Altoona, about 233 miles west of New York City, were soon summoned.

They arrived to find Mr. Mangione sitting at a table in the back of the restaurant, wearing a blue medical mask and looking at a laptop, according to a Pennsylvania police criminal complaint.

He initially gave them a fake ID, but when an officer asked Mr. Mangione whether he’d been to New York recently, he “became quiet and started to shake,” the complaint reads.

New York City’s police commissioner, Jessica Tisch, said at a Manhattan news conference that Mr. Mangione was carrying a ghost gun, a 3D-printed pistol and a 3D-printed silencer, like the weapon used to kill Thompson. He also was carrying the same fake ID the shooter had used to check into a New York hostel, along with a passport and other fraudulent IDs. 

The NYPD chief of detectives, Joseph Kenny, said Mr. Mangione also had a three-page, handwritten document that shows “some ill will toward corporate America.”

The document also included a line in which Mr. Mangione claimed to have acted alone.

“To the Feds, I’ll keep this short, because I do respect what you do for our country. To save you a lengthy investigation, I state plainly that I wasn’t working with anyone,” the document reads, according to The Associated Press.

It also had a line that reads, “I do apologize for any strife or traumas, but it had to be done. Frankly, these parasites simply had it coming.”

During his arraignment Monday night, Mr. Mangione reportedly disputed the prosecution’s contention that he was carrying about $10,000 in domestic and foreign currency and that he was a sophisticated criminal because his backpack was a “Faraday” bag capable of blocking electronic signals. 

“‘First, I don’t know where any of that money came from, I’m not sure if it was planted,” he reportedly said. “And also, that bag was waterproof, so I don’t know about criminal sophistication.'”