Accused CEO killer Luigi Mangione committed an act of domestic terrorism when he fatally shot a healthcare executive in Manhattan, US authorities allege.
Mr Mangione, 26, has been indicted by a grand jury in New York — part of the court process that formalises the charges against him.
He is now charged with 11 offences in that state, including murder in the first degree in furtherance of terrorism, murder in the second degree, and murder in the second degree as an act of terrorism.
"This was a frightening, well-planned, targeted murder that was intended to cause shock and attention and intimidation," Manhattan District Attorney Alvin Bragg said.
Mr Mangione is accused of shooting Brian Thompson, the 50-year-old CEO of major insurer UnitedHealthcare, just before the company's annual investor conference on December 4.
Asked why Mr Mangione was charged with a terrorism-related offence, Mr Bragg said it was "not an ordinary killing".
"This was a killing that it was intended to evoke terror, and we've seen that reaction," he told a media conference.
The indictment documents allege the killing was "intended to intimidate or coerce a civilian population, influence the policies of a unit of government by intimidation or coercion, and affect the conduct of a unit of government".
If convicted, Mr Mangione could be sentenced to life in prison with no possibility of parole.
'Appalling celebration of cold-blooded murder'
The crime triggered an outpouring of public anger with America's corporate health insurance sector, and a wave of support for the killer.
New York City Police Commissioner Jessica Tisch used the media conference to lambaste what she called "a shocking and appalling celebration of cold-blooded murder".
"Social media has erupted with praise for this cowardly attack," she told said.
"People ghoulishly plastered posters threatening the CEOs, other CEOs, with an 'X' over Mr Thompson's picture as though he was some sort of a sick trophy.
"And yesterday, the New York Post reported that some extreme activists were circulating a deck of cards with other 'most wanted CEOs' to be targeted for assassination.
"These are the threats of a lawless, violent mob who would trade in their own vigilantism for the rule of law that protects us all."
Police have previously said Mr Mangione was found with a handwritten "manifesto" that criticised corporate America, as well as a 'ghost gun' that matched the bullet casings found at the crime scene.
They have now confirmed the words "deny" and "depose" were written on two of those casings, and the word "delay" was written on a bullet found at the scene.
The phrase "delay, deny, defend" is frequently used in the US to describe the tactics insurers are suspected of using to avoid paying clients.
Friends have said Mr Mangione suffered a debilitating back injury while surfing in Hawaii, and detectives were investigating whether his experience with health insurance could have formed part of a motive.
But UnitedHealthcare later said Mr Mangione was not one of its clients.
Mr Mangione was arrested at a McDonald's restaurant in central Pennsylvania on December 9.
Police allege he was found with a nine-millimetre handgun with a 3D-printed receiver, two ammunition magazines, multiple live cartridges, a homemade silencer and a fake ID he had used to check into a New York hostel before the killing.
He remains in custody in that state. He is due to face a local court on Thursday, local time, for an extradition hearing.
"We have indications that the defendant may waive that hearing, in which case he will be brought to New York forthwith," Mr Bragg said.
