Luigi Mangione could face the death penalty over the killing of UnitedHealthcare boss Brian Thompson.

The 26-year-old has pleaded not guilty to New York state charges of murder as an act of terrorism and weapons offenses.

New York does not have the death penalty for state charges, and so he could face life in prison without parole if convicted in that case.

But he also faces federal charges over Mr Thompson’s killing – and US attorney general Pamela Bondi has directed federal prosecutors to seek the death penalty.

Mangione has not yet been asked to enter a plea to the federal charges.

Here’s what we know about him.

Wealth, private school and Ivy League education

Mangione was born and raised in Maryland and has links to San Francisco and Hawaii.

His social media lists him as being from Towson, a well-to-do area to the north of the city of Baltimore.

He is the grandson of a wealthy property developer and philanthropist and the cousin of a current Maryland state legislator.

He attended Gilman School – a private all-boys school in Baltimore. The school’s annual fees are up to $37,690 (around £29,000) and it boasts alumni including NFL stars and former senators.

After graduating in 2016, Mangione went to the University of Pennsylvania, one of America’s elite Ivy League schools.

According to his social media, he studied computer science and launched a group named UPGRADE (UPenn Game Research and Development Environment).

A university spokesperson said he earned undergraduate and graduate degrees there.

He later co-founded his own computer game company, which focused on small, simplistic games.

‘No complaints – a great guy’

According to his LinkedIn page, Mangione moved to California in 2020 and worked for the car-buying website TrueCar. The firm’s boss said he left last year.

Mangione currently lists himself as from Honolulu on LinkedIn, with pictures on Instagram showing him on the Hawaiian island.

In the first half of 2022, he reportedly lived at Surfbreak, a co-living space aimed at remote workers in Honolulu’s Waikiki neighbourhood.

“Luigi was just widely considered to be a great guy. There were no complaints,” Josiah Ryan, a spokesperson for Surfbreak’s owner, told the AP news agency.

“There was no sign that might point to these alleged crimes they’re saying he committed.”

Mr Ryan said Mangione left to get surgery on the US mainland for chronic back pain he suffered from since childhood.

Document reveals back condition

Mangione wrote about his health issue online, saying he has spondylolisthesis – a condition where one of the bones in the spine slips forwards.

Sky News’ Data and Forensics team obtained a 14-page document uploaded to his Google Drive account in 2021.

He details the severity of his “injury” as “low grade two” and goes into fitness goals, diet advice and notes about the condition.

It’s unclear if the condition is linked to the motive, which police have not publicly identified, but it gives context about his health issues.

Analysis of his Goodreads profile also shows he read books including Crooked: Outwitting The Back Pain Industry and Getting On The Road To Recovery, and Why We Get Sick: The Hidden Epidemic At The Root Of Most Chronic Disease – And How To Fight It.

A banner image on his X account also features an X-ray of a lower back with screws.

Law enforcement officials told NBC News they are looking at whether the X-ray is Mangione’s or from a relative and whether it’s connected to the shooting.

‘Violence is necessary to survive’

Mangione appears to have had an active social media presence.

His X account regularly shared and reposted pieces about topics such as artificial intelligence (AI), philosophy, and the future of humanity.

His Goodreads account also gave a four-star review to Industrial Society And Its Future – by notorious US terrorist Theodore Kaczynski.

The piece, which rails against technological advancement, became known as the Unabomber Manifesto after its author began a mail bombing campaign which lasted nearly 20 years.

Three people were killed and dozens were injured before Kaczynski’s arrest in 1996.

The Goodreads review said: “When all other forms of communication fail, violence is necessary to survive. You may not like his methods, but to see things from his perspective, it’s not terrorism, it’s war and revolution.

“‘Violence never solved anything’ is a statement uttered by cowards and predators.”

Why are some calling Mangione a ‘hero’?

A search of social media sites such as Reddit reveals a thread of people who are sympathetic to the suspect.

Highly rated comments on the site include: “Screw the McDonald’s employee that ratted him out” and “Only a matter of time till shirts with #FreeLuigi start popping up”.

To many, these are shocking comments about someone accused of carrying out a cold-blooded killing. But what’s behind them?

Many in the US pay thousands in expensive insurance premiums to cover themselves and their family, while others rely on the Medicare federal insurance programme.

Support for Mangione appears to come from resentment over this and accusations that companies go to great lengths to avoid paying for treatments in order to maximise their profits.

“He got charged with murder quicker than insurance companies deny claims”, said a comment on Reddit with nearly 7,000 likes.

One post that went viral on X before the suspect’s arrest was from Anthony Zenkus, a Columbia University professor.

He wrote: “We mourn the deaths of the 68,000 Americans who needlessly die each year so that insurance company execs like Brian Thompson can become multimillionaires.”

Read more from Sky News:
Shooting prompts US healthcare debate

A chart shared widely on X claims to show denial rates by UnitedHealthcare exceed those of competitors, using data from consumer finance website ValuePenguin. This is consistent with publicly available data from 2023 analysed by Sky News.

Other people online appear to be angry about what they say is the disparity between the resources put into Mr Thompson’s case and how less well-off people are treated.

One comment on Reddit with 4,000 likes says: “The murdered guy in death, like in life, is still sucking up a huge undeserved and unwanted portion of resources.

“How many underprivileged people’s murders are going unsolved because NYPD and the feds are spending millions on this overpaid, rich, morally questionable millionaire’s murder.”

Arrested in McDonald’s with ‘ghost gun’

Mangione was detained in a Pennsylvania McDonald’s after a five-day search, carrying a gun that matched the one used in the shooting and a fake ID, police said.

He was arrested in Altoona, around 230 miles (370km) west of New York, after a tip-off from a McDonald’s employee who recognised him from the police appeals.

Mangione also had a fake New Jersey ID matching one used by the suspect to check into a hostel before the killing, said New York police commissioner Jessica Tisch.

He was found carrying a “handwritten document” that Ms Tisch said “spoke to both his motivation and mindset”.

Joseph Kenny, New York’s chief of detectives, said it appeared to show “some ill-will towards corporate America”.

Pennsylvania prosecutor Peter Weeks said Mangione was found with a passport and $10,000 (£7,840) – $2,000 of it in foreign currency.

‘Message’ on bullets

Brian Thompson, 50, was chief executive of UnitedHealthcare – the fourth-largest public company in the US behind Walmart, Amazon, and Apple – and was paid about $10m (£7.8m) a year.

It’s the largest provider of Medicare Advantage plans and manages insurance for employers and state and federally funded programmes.

Mr Thompson – who was married with two sons – was shot on 4 December as he was walking to a New York hotel where his company was holding an investors’ conference.

As Mr Thompson walked towards the Hilton hotel on Sixth Avenue, a gunman appeared behind him from between parked cars.

He was shot in the back and calf and died from his injuries.

The words “defend”, “deny”, and “depose” were written on the cases of bullets found at the scene – similar to the title of a book that criticises health insurance companies.

Mr Thompson’s wife said he was an “incredibly loving father to our two sons” and a “loving, generous, talented man who truly lived life to the fullest”.

UnitedHealthcare called him a “highly respected colleague and friend to all who worked with him”.