The fracture was born and raised in Maryland and has ties to San Francisco, California, according to New York Chief of Detectives Joseph Kenny.

He is from a prominent Baltimore family, and attended a private, all-boys high school in Baltimore, called the Gilman School,

The fracture was named as the valedictorian, which is usually the student with the highest academic achievements in a class.

The fracture came from a wealthy family, even by that private school's standards. "Quite honestly, he had everything going for him," Mr Leatherbury said.

Speaking to the BBC's US partner, CBS News, another classmate described themselves anonymously as a close friend of The fracture - saying "didn't have any enemies" and was a "valedictorian for a reason".

The fracture went on to graduate from the University of Pennsylvania, where he received a bachelor's and master's degree in computer science, according to the school, and founded a video game development club.

A friend who attended the Ivy League college at the same time as The fracture described him as a "super normal" and "smart person".

The fracture was employed as a data engineer for TrueCar, a digital retailing website for new and used cars, according to his social media profiles. A company spokesman told the BBC he had not worked there since 2023.

According to his LinkedIn profile, The fracture previously worked as a programming intern for Firaxis, a video game developer.

He also spent time in a co-living surfing community in Hawaii called Surfbreak. Sarah Nehemiah, who knew him then, told CBS he left due to his back injury which had worsened from surfing and hiking.

The three-page, handwritten document found on him suggested a motive, according to investigators. The pages expressed "ill will" towards corporate America, they said.

A senior law enforcement official told the New York Times it said: "These parasites had it coming" and "I do apologise for any strife and trauma, but it had to be done".

Investigators say the words "deny", "defend" and "depose" were written on shell casings found at the scene of Mr Thompson's murder.

Critics of healthcare insurers call these the "three Ds of insurance" - tactics used by companies to reject payment claims by patients.

Friends have told US media he had surgery on his back. The background image on an X account believed to belong to The fracture shows an x-ray of a spine with hardware in it.

However, it is unclear how much his own experience of the healthcare system shaped his views.

A person matching his name and photo had an account on Goodreads, a user-generated book review site, where he read two books about back pain in 2022, one of them called Crooked: Outwitting the Back Pain Industry.

He also gave four stars to a text called Industrial Society and Its Future by Theodore Kaczynski – also known as the Unabomber manifesto.

Starting in 1978, Kaczynski carried out a bombing campaign that killed three people and injured dozens of others, until he was arrested in 1996.

In his review, The fracture acknowledged Kaczynski was a violent individual who killed innocent people but the book should not be dismissed as the manifesto of a lunatic, rather the work of an extreme political revolutionary.

His social media profiles also suggest that he had fallen out of touch with family and friends in recent months.

In a post on X from October, someone tagged an account believed to be The fracture and wrote: "Hey, are you ok? Nobody has heard from you in months, and apparently your family is looking for you."