Luigi Mangione, the suspect accused of murdering UnitedHealthcare CEO Brian Thompson on Dec. 4 in Manhattan, was extradited Thursday from Pennsylvania back to New York, where he faces state and now federal charges.

Mangione, 26, was flown out of Pennsylvania on Thursday to face murder charges in New York. He landed at a Long Island airport, where a New York Police Department helicopter took him to Manhattan on Thursday afternoon.

Mangione could potentially face the death penalty if federal prosecutors decide to pursue that route, though the last execution in New York was in 1963, according to Ret. NYPD Det. Teresa Leto.

“The likelihood is slim,” Leto said, adding: “I’d be shocked…but anything can happen.”

UNITEDHEALTHCARE CEO MURDER SUSPECT LUIGI MANGIONE INDICTED IN NEW YORK

She added that Mangione “has a lot going for him, just because he’s young,” and said she would be surprised if federal prosecutors pursued the death penalty against a 26-year-old suspect.

Federal court documents filed Thursday afternoon show he is facing two counts of stalking, one count of murder using a firearm and one count of using a firearm in the commission of a crime in the Southern District of New York.

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“The federal government’s reported decision to pile on top of an already overcharged first-degree murder and state terror case is highly unusual and raises serious constitutional and statutory double jeopardy concerns,” his New York defense attorney, Karen Friedman Agnifilo, told Fox News. “We are ready to fight these charges in whatever court they are brought.”

Following a federal court hearing in Manhattan that concluded after 3 p.m. Thursday, Agnifilo declined comment but added that Mangione appreciates the support he has received.

“I will say this over and over again: the radicalization that is taking place across our country, we cannot ignore,” New York City Mayor Eric Adams said during a press gaggle after Mangione arrived in New York. “When you see an incident that took place so now stories when you witnessed a shooting took place or the school campus by now a young girl, that is the continuation of our young people are crying out for help.”

Edward Y. Kim, the Acting United States Attorney for the Southern District of New York, said in a statement Thursday that the case brought by Manhattan District Attorney Alvin Bragg’s office is expected to proceed to trial before the federal case.

Officials flew Mangione to New York after he attended two court proceedings at the Blair County Courthouse in Hollidaysburg, Pennsylvania, on Thursday morning.

“We have an obligation not only to make apprehensions after an incident of this magnitude, but to do far more to prevent the open question.”

— Eric Adams

NYPD officers were seen sitting in the entire front row of the room where Mangione’s court proceedings took place in the Blair County Courthouse.

Several people outside the courthouse held signs that read “Deny, Defend, Depose,” the same message that Mangione allegedly left on shell casings at the scene of Thompson’s murder and words that are commonly used among insurance providers when they reject claims. 

Read the federal complaint. Mobile users click here

The court covered his extradition hearing, as well as a preliminary hearing for his other firearms and fraudulent ID-related charges in Pennsylvania. The first hearing regarding his state charges ended around 9:20 a.m. 

The suspect’s Altoona-based attorney, Thomas Dickey, spoke to Mangione, who nodded his head, ahead of the extradition hearing portion of Thursday’s proceedings.

Mangione’s defense officially filed his extradition waiver later on Thursday morning, which Judge David Consiglio signed, approving the suspect’s return to Manhattan.

“Our intention is to keep our case active,” Blair County District Attorney Peter Weeks said Thursday after the conclusion of Mangione’s court proceedings, adding that the suspect’s charges in New York are the “primary” case, and Blair County officials will continue to work with New York officials.

Read the extradition waiver. Mobile users click here.

New York prosecutors say Mangione plotted to travel to New York; find Thompson, a Minnesota resident in town for UnitedHealthcare’s annual shareholder conference; and kill him. Mangione allegedly shot Thompson from behind with a 3D-printed ghost gun and suppressor. 

Bragg on Tuesday announced that a grand jury indicted Mangione on one count of first-degree murder, in furtherance of terrorism; two counts of second-degree murder; two counts of second-degree criminal weapons possession; four counts of third-degree criminal weapons possession; one count of fourth-degree criminal weapons possession; and one count of second-degree criminal possession of a forged instrument.

Prosecutors say Mangione fled New York City within an hour after the crime and traveled to Altoona, Pennsylvania.

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Altoona police arrested Mangione in a McDonald’s five days later on Dec. 9 after receiving a tip from an employee. The suspect allegedly presented local police with a fake ID and appeared to start shaking when they asked if he had been in New York recently.

Police said the suspect took a bus from New York City to Philadelphia, and then from Philadelphia to Pittsburgh and on to Altoona — a rust-belt town nestled between Pittsburgh and Harrisburg.

Officials also found a handwritten manifesto condemning the health care industry, as NYPD Chief of Detectives Joseph Kenny previously told Fox News. The manifesto specifically mentioned UnitedHealthcare.

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While officials have not commented on an official motive, the public has speculated that the suspect had strong grievances with both the health care insurance industry.

Watch: Eric Adams discusses Luigi Mangione extradition

The 26-year-old suspect is originally from Maryland and has recently lived in California and Hawaii. Mangione graduated valedictorian from the Gilman School, a private, all-boys high school in Baltimore, in 2016. He went on to receive his bachelor’s and master’s degrees in computer science from the University of Pennsylvania in 2020.

The day after his arrest in Altoona, on Dec. 10, Mangione announced that he would not waive extradition.

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“We did not waive extradition and we’re contesting extradition. We are going to fight this along the rules and with the constitutional protections that my client has,” Dickey told reporters outside the Blair County Courthouse on Dec. 10.

Fox News’ David Hammelburg, Alexis McAdams, and Maria Parnovich contributed to this report.