NEW YORK, Dec 18 — Luigi Mangione sought to "sow terror” by shooting dead UnitedHealth Group executive Brian Thompson on a Manhattan street this month, a New York prosecutor said on Tuesday in announcing Mangione had been indicted for murder.

A grand jury indicted Mangione on 11 counts, including first-degree murder and murder as a crime of terrorism, Manhattan District Attorney Alvin Bragg told reporters. Mangione, 26, would face a mandatory sentence of life in prison without the possibility of parole if convicted on all counts.

"This was a frightening, well-planned, targeted murder that was intended to cause shock and attention and intimidation,” Bragg told reporters. "The intent was to sow terror.”

Mangione’s defence lawyer in New York, Karen Friedman Agnifilo, declined to comment.

Ivy League-educated Mangione was charged with murder on Dec. 9 for the killing of Thompson outside a Manhattan hotel before a company conference, following a five-day manhunt.

Mangione is currently being held on gun charges in Pennsylvania, where he was arrested last week at a McDonald’s restaurant in the city of Altoona.

Bragg said he had indications that Mangione may waive his right to contest his extradition to New York. A hearing over Mangione’s extradition is scheduled for Thursday in Pennsylvania.

The killing of Thompson has ignited an outpouring of anger from Americans struggling to receive and pay for medical care.

Americans pay more for health care than any other country, with spending on insurance premiums, out-of-pocket co-payments, pharmaceuticals and hospital services on the rise in recent years, government data shows.

The words "deny,” "defend” and "depose” were written on shell casings found at the Thompson murder scene, several news outlets reported, evoking the title of a book critical of the insurance industry.

Mangione has been celebrated in some circles, and more than a thousand donations have poured into an online fundraiser for his legal defence.

New York Police Commissioner Jessica Tisch said any attempt to rationalize Mangione’s alleged actions was "vile.”

"There is no heroism in what Mangione did,” Tisch told reporters. "We don’t celebrate murders and we don’t lionize the killing of anyone.”

The indictment accused Mangione of murdering Thompson with the intent to "influence the policy of a unit of government by intimidation or coercion.”

Mangione suffered from chronic back pain that affected his daily life, according to friends and social media posts, though it is unclear whether his own health played a role in the shooting.

UnitedHealth Group said last week Mangione was not a customer of the health insurer. — Reuters