Mangione faces new federal charges in the US that carry the possibility of the death penalty.
Luigi Mangione, the suspect in the murder of UnitedHealthcare CEO Brian Thompson, appeared in court in New York to answer new federal charges including murder and racketeering.
Mangione's arraignment on Thursday was followed by his transfer to New York from Pennsylvania after he waived his right to extradition.
Leg shackled and wearing a blue sweater and beige skirt, Mangione did not say much during the 15-minute hearing before US Attorney Katharine Parker in Manhattan.
The 26-year-old Ivy League graduate, who had previously been indicted on multiple federal charges, is charged with first-degree murder, two counts of second-degree burglary and one count of first-degree assault, according to an unofficial complaint.
The state's charges led to Mangione receiving the death penalty, if prosecutors sought it.
Mangione's attorney, Karen Friedman Agnifilo, said it was “very unusual” for a defendant to face federal and state charges at the same time.
“Honestly, I have never seen anything like what is happening here,” said Friedman Agnifilo.
According to the criminal complaint, Mangione left Georgia for New York “with the intention of killing Brian Thompson”.
The pamphlet Mangione had with him when he was arrested at a McDonald's in Altoona, Pennsylvania contained several handwritten pages that “expressed hatred toward health insurance companies and wealthy executives,” according to the complaint.
An entry in August said it was “targeting an insurance company” because it “checked every box”, while an entry in October described the target of a “wack” CEO of an insurance company”, according to the complaint.
Police said the words “delay,” “refusal” and “removal” were written on the bullets found at the scene of the murder, recalling words used to describe insurance policies to avoid payment.
While Mangione was being tried in court, his supporters gathered outside holding signs reading “Health over wealth” and “Luigi set us free”.
James Dennehy of the FBI's New York Field Office said Magione's actions were “well-planned and murderous”.
“This proposed plot shows how society views people – to think that killing is the right way to deal with grievances,” Dennehy said.