He was arrested on Monday at a McDonald’s in Altoona, Pennsylvania, and was allegedly in possession of a gun, bullets, multiple fake IDs and cash.

Mr Mangione also had a handwritten document that expressed “ill will” towards corporate America and included passages such as “frankly, these parasites had it coming”, according to police.

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.

Mr Mangione comes from a prominent family in the Baltimore area who are known for businesses including country clubs, nursing homes and a radio station according to local media.

The suspect’s paternal grandparents, Nicholas and Mary Mangione, were real estate developers who purchased the Turf Valley Country Club in 1978 and Hayfields Country Club in Hunt Valley in 1986.

Shortly after Mr Mangione was charged, his cousin, Republican state lawmaker Nino Mangione, released a statement saying the family was “shocked and devastated”.

“We offer our prayers to the family of Brian Thompson and we ask people to pray for all involved”, the statement read.

Thomas Maronick, a defence attorney who knows members of the family, told the BBC of his shock at the charges.

“You wouldn’t think someone of privilege or means from a family that’s known for doing so much for the community would do something like this.”

Mr Mangione attended a private, all-boys high school in Baltimore, called the Gilman School, where he was valedictorian, an accolade usually bestowed on the student with the highest academic achievements in a class.

Speaking to the BBC’s US partner, CBS News, one of his classmates said Mr Mangione “didn’t have any enemies” and was a “valedictorian for a reason”.