Police detail horrifying ‘manifesto’ found on Luigi Mangione during arrest for murder of UnitedHealthcare's CEO

The man arrested and charged with the murder of UnitedHealthcare CEO Brian Thompson had on him a 'manifesto' ranting about the insurance industry.

At 9.15am yesterday (December 9), Luigi Mangione was taken into custody in connection to the 50-year-old's death five days earlier (December 4).

What we know about UnitedHealthcare CEO Brian Thompson's murder

Thompson, a father-of-two, was walking to an insurance conference in New York City when he was gunned down in the streets outside of the Hilton Hotel, in Manhattan, with the suspect believed to have been 'lying in wait' for up to five minutes beforehand.

Thompson was rushed to Mount Sinai Hospital in a critical condition but was later pronounced dead upon arrival.

The 26-year-old suspect is understood to have cycled away on an electric bike into Central Park, where a bag was discarded with Monopoly money inside it as well as a jacket.

Thompson was shot outside a New York City hotel (Spencer Platt/Getty Images)

'Manifesto' and other belongings of Mangione suspect found by police

According to police sources cited by the New York Post, police also recovered a handwritten note during Mangione's arrest which accused insurance companies of only caring about the 'immense profit' they made at the expense of American customers.

The 'manifesto' was allegedly addressed to 'the Feds', and read: “The reality is, these [companies] have gotten too powerful, and they continue to abuse our country for immense profit."

The suspect is also said to have written that he'd worked alone, and apologized in the note for any trauma he caused, but said it 'had to be done'.

“Frankly, these parasites simply had it coming," he wrote, according to the sources.

The note was found along with a 3D-printed pistol and silencer, a loaded Glock magazine, and multiple fake IDs in a backpack when Mangione was arrested at a McDonald’s in Altoona, Pennsylvania.

Speaking to The Daily Beast about the Monopoly money, which has also been linked to the suspect, Dr. Carole Lieberman stated that she believed the gunman had 'planned to scatter the Monopoly money around the CEO's body after he shot him, but he forgot to take the bills out of his backpack'.

Police put out an appeal for information after a suspect appeared on CCTV (DCPI)

The psychiatrist explained that it is of her understanding that the Monopoly money is meant to liken UnitedHealthcare to a monopoly, and suggested it symbolized that the insurance firm is a 'ripoff that steals money from patients'.

Retired FBI agent Jennifer Coffindaffer told the publication: “To me, this seems like somebody far beyond just a personal situation, that he lost a family member or a loved one due to lack of being insured. This seems much larger, like a vigilante, somebody who is well prepared to make a big statement and that he blames UnitedHealthcare in this situation.”