UnitedHealthcare CEO murder suspect Luigi Mangione complained about back surgery before slaying

The former Ivy League computer scientist charged in the ambush shooting death of UnitedHealthcare CEO Brian Thompson had struggled with back pain and the fallout from a spinal surgery, according to reports.

Mangione lived there for at least six months in 2022, according to former roommate RJ Martin, who told the outlet that Mangione's lower back problems affected him for years due to misaligned vertebrae that could sometimes pinch his spinal cord.

Mangione told his roommate he'd gotten surgery after moving out of the Surfbreak co-op where they lived together, then "he went radio silent."

NYPD Chief of Detectives Joseph Kenny told Fox News' Neil Cavuto Tuesday that Mangione specifically mentioned UnitedHealthcare and the shareholder conference where Thompson was headed at the time of the shooting in his alleged manifesto.

Mangione had allegedly written online about his injury, the chief said, and investigators were looking into whether the health insurance industry had denied a claim from him or withheld some kind of care.

NYPD detectives received more than 200 tips, he said, but none of them mentioned Mangione by name.

"He knew that dating and being physically intimate with his back condition wasn't possible," he told the paper. "I remember him telling me that, and my heart just breaks."

Police have not immediately publicized a potential motive for the murder but alleged that Mangione admitted to the crime in writing and left behind other clues, including bullet casings with the words "deny," "defend" and "depose" on them and a backpack full of Monopoly money.

Mangione appeared to rationalize the actions of Ted Kaczynski, the Unabomber, on Goodreads, a book-based social media site. Writing about the bomber's manifesto, "Industrial Society and Its Future," he quoted another online "take that [he] found interesting."

"When all other forms of communication fail, violence is necessary to survive," he wrote. "You may not like his methods, but to see things from his perspective, it's not terrorism, it's war and revolution."

Martin told CivilBeat that Mangione had suggested Kaczynski's manifesto to their local book club. The reading material was so "painful to read" that it ended up breaking apart the club, he told the outlet. But Mangione, writing on Goodreads, felt that it had predicted the future.

"It's easy to quickly and thoughtlessly write this off as the manifesto of a lunatic, in order to avoid facing some of the uncomfortable problems it identifies," he wrote. "But it's simply impossible to ignore how prescient many of his predictions about modern society turned out."

Responding officers, including a rookie cop who received praise from leaders in New York and Pennsylvania, immediately recognized Mangione as the suspect wanted in connection with the New York City ambush shooting of UnitedHealthcare CEO Brian Thompson, authorities said.

WATCH: McDonald's customer recognized suspect's backpack, jacket

Prosecutors alleged in court that he had the suspected murder weapon, a so-called ghost gun with 3D-printed parts and a suppressor, the same fake ID used to check into a Manhattan hostel before the shooting, $10,000 in American and foreign cash, and a "Faraday bag" used to block cell service.

Mangione told the judge that the cash wasn't his.

"I don't know where that money came from," he said. "It must have been planted. I don't have that kind of cash."

The bag, he added, was just a waterproof bag. An online search found several companies selling Faraday containers describe them as also being waterproof.

Surveillance video taken outside a Midtown Manhattan Hilton hotel shows a masked assassin sneak up behind Thompson on the sidewalk around 6:45 a.m. last Wednesday, Dec. 4. 

Thompson was on his way to a shareholder conference at the venue set to begin later that morning when the gunman opened fire from behind.

Surveillance images taken from a hostel he stayed at near Central Park circulated widely online as police launched an interstate manhunt for the suspect.

Mangione is facing a slew of charges in New York in connection with the murder, as well as additional charges, including unlawful possession of a firearm and a forged ID, in Pennsylvania.

He graduated with bachelor and master's degrees in computer science from the University of Pennsylvania in 2020 and comes from a prominent Baltimore family.

He also attended the Gilman School, a private prep school in the city, where he was valedictorian in 2016.

The notes left on the bullet casings found at the crime scene have drawn comparisons to the book "Delay, Deny, Defend: Why Insurance Companies Don't Pay Claims and What You Can Do About It" - speculation swirled that the slaying may have grown out of resentment for a denied claim.

The book was not found on Mangione's Goodreads account when accessed before it was set to private Monday.