UnitedHealthcare CEO's killing: Luigi Mangione pleads not guilty to state murder, terror charges

NEW YORK CITY (FOX 9) - Luigi Mangione pleaded not guilty on Monday to murder and terror charges in the killing of UnitedHealthcare CEO Brian Thompson. 

The arraignment was for his state case. This case will run parallel to his federal prosecution. 

Mangione pleads not guilty 

What we know: Mangione was shackled when he pleaded not guilty to the state charges against him on Monday. The 26-year-old was formally charged last week by the Manhattan district attorney with multiple counts of murder, including murder as an act of terrorism. 

What they're saying: During the hearing, one of Mangione’s attorneys told the judge that government officials, including New York Mayor Eric Adams, have turned Mangione into a political pawn, robbing him of his rights as a defendant and tainting the jury pool.

"I am very concerned about my client’s right to a fair trial," said Karen Friedman Agnifilo.

"This is a young man," she said. "He is being treated like a human pingpong ball between warring jurisdictions here."

His initial appearance in New York State Supreme Court was preempted by federal prosecutors bringing their own charges over the shooting.

The federal charges could carry the possibility of the death penalty, while the maximum sentence for the state charges is life in prison without parole. Prosecutors have said the two cases will proceed on parallel tracks, with the state charges expected to go to trial first.

Killing of Brian Thompson

The backstory: According to authorities, Mangione shot and killed Thompson on the morning of Dec. 4 as he was walking to an investor conference in midtown Manhattan.

Mangione was arrested inside 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 also was carrying a notebook expressing hostility toward the health insurance industry and especially wealthy executives, according to federal prosecutors.

Mangione, an Ivy-league graduate from a prominent Maryland family, appeared to have cut himself off from family and friends in recent months. He posted frequently in online forums about his struggles with back pain. He was never a UnitedHealthcare client, according to the insurer.

Thompson, a married father of two children from Maple Grove, Minnesota, worked at the giant UnitedHealth Group for 20 years and became CEO of its insurance arm back in 2021.

Dig deeper: Thompson's killing has prompted some to voice their resentment at U.S. health insurers, with Mangione serving as a stand-in for frustrations over coverage denials and hefty medical bills. It also has sent shockwaves through the corporate world, rattling executives who say they have received a spike in threats.