The suspect in the killing of UnitedHealthcare’s CEO was whisked back to New York on a plane and by helicopter Thursday to face new federal charges of stalking and murder, which could bring the death penalty if he's convicted.

Luigi Mangione agreed to return to New York after a morning court appearance in Pennsylvania, where he was arrested last week five days after the shooting of Brian Thompson. Mangione appeared in a Manhattan federal court for an afternoon hearing where a magistrate ordered he be detained.

After his Pennsylvania court hearing, Mangione was immediately turned over to at least a dozen New York Police Department officers who were in the courtroom and led him to a plane bound for Long Island. He then was flown to a Manhattan heliport, where he was walked slowly up a pier by officers with assault rifles.

The federal complaint unsealed Thursday charges him with two counts of stalking and one count each of murder through use of a firearm and a firearms offense. One of the federal charges, murder by firearm, could bring the possibility of the death penalty if he is convicted. Federal prosecutors have not said whether they will pursue such a punishment.

In a New York state indictment filed earlier this week, Mangione was charged 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.

In federal court Thursday, Mangione shifted his head but otherwise did not react when the magistrate read the part of the complaint accusing him of killing Thompson.

His attorney said dealing with both the state and federal cases puts the defense in a highly unusual situation. “Frankly I’ve never seen anything like what is happening here,” said Karen Friedman Agnifilo.

She argued the new federal charges appeared to be “in conflict” with the New York charges.

“Speaking generally, we’ve had state prosecutions and federal prosecutions proceed as parallel matters in conversations with our law enforcement counterparts,” Manhattan District Attorney Alvin Bragg said at an unrelated press conference.

The Manhattan DA's office said they are coordinating with federal authorities on the timing and logistics of Mangione's case.

According to the Federal Bureau of Prisons, Mangione is in custody at the Metropolitan Detention Center in Brooklyn.

Mangione’s next appearance in federal court is Jan. 18. However, an appearance on the New York charges could happen sooner.

The 26-year-old Ivy League graduate is accused of ambushing and shooting Brian Thompson on Dec. 4 outside a Manhattan hotel where the head of the United States’ largest medical insurance company was walking to an investor conference.

Authorities have said Mangione was carrying the gun used to kill Thompson, a passport, fake IDs and about $10,000 when he was arrested while eating breakfast on Dec. 9 at a McDonald’s in Altoona, Pennsylvania.

Mangione, who initially fought attempts to extradite him, made two brief court appearances Thursday, first waiving a preliminary hearing on forgery and firearms charges before agreeing to be sent back to New York.

Investigators believe Mangione was motivated by anger toward the U.S. health care system and corporate greed. But he was never a UnitedHealthcare client, according to the insurer.

According to the federal complaint, a notebook Mangione was carrying when he was arrested included several handwritten pages expressing hostility toward the health insurance industry and wealthy executives in particular.

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.

The killing ignited 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.

Video showed a masked gunman shooting Thompson, 50, from behind and then firing several more shots. The suspect eluded police despite authorities widely circulating photos of his unmasked face until Mangione was captured in Altoona, about 277 miles (446 kilometers) west of New York.

Mangione, a computer science graduate from a prominent Maryland family, was carrying a handwritten letter that called health insurance companies “parasitic” and complained about corporate greed, according to a law enforcement bulletin obtained by The Associated Press last week.

One of his lawyers has cautioned the public against prejudging the case.

Mangione 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 his family and close friends in recent months. His family reported him missing in San Francisco in November. His relatives have said in a statement that they were “shocked and devastated” by his arrest.

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 the giant UnitedHealth Group for 20 years and became CEO of its insurance arm in 2021.