NEW YORK (AP) — The man accused of killing UnitedHealthcare’s CEO was whisked back to New York by plane and helicopter Thursday to face new federal charges of stalking and murder, which could bring the death penalty if he’s convicted.

Luigi Mangione was held without bail following a Manhattan federal court appearance, capping a whirlwind day that began in Pennsylvania, where he was arrested last week in the Dec. 4 attack on Brian Thompson.

The 26-year-old Ivy League graduate had been expected to be arraigned Thursday on a state murder indictment in a killing that at once rattled the business community and galvanized some health insurance critics, but the federal charges preempted that appearance. The cases will now proceed on parallel tracks, prosecutors said, with the state charges expected to go to trial first.

Mangione, shackled at the ankles and wearing dress clothes, said little during the 15-minute proceeding as he sat between his lawyers in a packed federal courtroom.

He nodded as a magistrate judge informed him of his rights and the charges against him, occasionally leaning forward to a microphone to tell her he understood.

After the hearing, a federal marshal handed Mangione’s lawyers a bag containing his belongings, including the orange prison jumpsuit he had worn to court in Pennsylvania.

Mangione had been held in Pennsylvania since his Dec. 9 arrest while eating breakfast at a McDonald’s in Altoona, about 233 miles (37 kilometers) west of Manhattan.

At a hearing there Thursday morning, Mangione agreed to be returned to New York and was immediately turned over to at least a dozen New York Police Department officers who took him to an airport and a plane bound for Long Island.

He then was flown to a Manhattan heliport, where he was walked slowly up a pier by a throng of officers with assault rifles — a contingent that included New York City Mayor Eric Adams and Police Commissioner Jessica Tisch.

The federal complaint filed Thursday charges Mangione with two counts of stalking and one count each of murder through use of a firearm and a firearms offense. Murder by firearm carries the possibility of the death penalty, though federal prosecutors will determine whether to pursue that path in coming months.

In a state court indictment announced earlier this week, Manhattan District Attorney Alvin Bragg’s office charged Mangione with murder as an act of terrorism, which carries a possible sentence of life in prison without parole. New York does not have the death penalty.

Mangione’s lawyer, Karen Friedman Agnifilo, said it’s a “highly unusual situation” for a defendant to face simultaneous state and federal cases.

“Frankly I’ve never seen anything like what is happening here,” said Friedman Agnifilo, a former top deputy in the Manhattan district attorney’s office.

She reserved the right to seek bail at a later point and declined to comment as she left the courthouse.

Mangione, of Towson, Maryland, is accused of ambushing the 50-year-old Thompson as the executive arrived to a Manhattan hotel for an investor conference.

Surveillance video showed a masked gunman shooting Thompson from behind. Police say the words “delay,” “deny” and “depose” were scrawled on the ammunition investigators found at the scene, echoing a phrase commonly used to describe insurer tactics to avoid paying claims.

The gunman then pedaled a bicycle through Central Park, took a taxicab to a bus station and then rode the subway to a train station before fleeing to Pennsylvania, authorities said.

There, a McDonald’s customer noticed that Mangione looked like the person in surveillance photos police were circulating of the gunman, prosecutors said.

When he was arrested, they say, Mangione had the gun used to kill Thompson, a passport, fake IDs and about $10,000.

According to the federal complaint, Mangione also had a spiral notebook that included several handwritten pages expressing hostility toward the health insurance industry and wealthy executives. UnitedHealthcare is the largest health insurer in the U.S., though the insurer said Mangione was never a client.

An August entry said that “the target is insurance” because “it checks every box,” according to the filing. An entry in October “describes an intent to ‘wack’ the CEO of one of the insurance companies at its investor conference,” the document said.

Mangione initially fought attempts to return him to New York. In addition to waiving extradition Thursday, he waived a preliminary hearing on forgery and firearms charges in Pennsylvania.

The killing unleashed an outpouring of stories about resentment toward U.S. health insurance companies while also shaking corporate America after some social media users called the shooting payback.

Mangione, a computer science graduate from a prominent Maryland family, repeatedly posted on social media about how spinal surgery last year had eased his chronic back pain, encouraging people with similar conditions to speak up for themselves if told they just had to live with it.

In a Reddit post in late April, he advised someone with a back problem to seek additional opinions from surgeons and, if necessary, say the pain made it impossible to work.

“We live in a capitalist society,” Mangione wrote. “I’ve found that the medical industry responds to these key words far more urgently than you describing unbearable pain and how it’s impacting your quality of life.”

He apparently cut himself off from family and close friends in recent months. His family reported him missing in San Francisco in November.

Thompson, who grew up on a farm in Iowa, was trained as an accountant. A married father of two high-schoolers, he had worked at UnitedHealth Group for 20 years and became CEO of its insurance arm in 2021.