FEDERAL CHARGES, INCLUDING MURDER, THAT COULD RESULT IN THE DEATH PENALTY IF HE'S CONVICTED.

THIS MORNING, LUIGI MANGIONE IS BACK IN NEW YORK CITY TO FACE

CHARGES, LANDING THURSDAY AFTER BEING EXTRADITED FROM PENNSYLVANIA WHERE HE WAS

ARRESTED. THE 26-YEAR-OLD IS ACCUSED OF MURDERING UNITED HEALTHCARE CEO

BRIAN THOMPSON. HE WAS HANDCUFFED, SHACKLED, AND ESCORTED BY LAW

ENFORCEMENT. >> WE WANT TO SEND A VERY CLEAR, LOUD MESSAGE THAT THIS ACT OF

TERRORISM IS SOMETHING THAT WILL NOT BE TOLERATED IN THE CITY. >> Reporter: MANGIONE IS HIT WITH

STALKING AND A MURDER CHARGE THAT COULD CARRY THE DEATH

PENALTY. THAT'S ON TOP OF 11 STATE CRIMINAL CHARGES IN NEW YORK,

INCLUDING MURDER IN THE FIRST DEGREE IN THE FURTHERANCE OF TERRORISM.

THE NEWLY UNSEALED FEDERAL COMPLAINT ALSO REVEALS NEW

DETAILS IN THE INVESTIGATION, SAYING MANGIONE UNDERTOOK

EXTENSIVE EFFORTS TO IDENTIFY, PLACE UNDER SURVEILLANCE, AND TRACK THE VICTIM'S WHEREABOUTS

IN THE TIME PERIOD LEADING UP TO THE MURDER. IN THE HOURS BEFORE THE SHOOTING,

ON AT LEAST ONE OCCASION, THE SHOOTER WAS DEPICTED USING A

Cell phone. It does not specify who Mangione may have been talking to.

The documents detail what was inside the notebook that was recovered during his arrest at a

Pennsylvania McDonald's last week. According to the complaint,

Mangione had pages related to the healthcare industry.

He wrote, "The details are finally coming together, adding

the target is insurance because it checks every box." His day Thursday began in a

Pennsylvania courthouse where he told a judge he was waiving his

right to an extradition hearing. He was then immediately taken

into custody by New York law enforcement, driven to the airport where a plane was

waiting. Ultimately, a helicopter brought him to Lower Manhattan

and his first appearance before a federal judge. He has not entered a plea in

either the state or federal case. >> We're going to respectfully

decline to make any comment at this time. >> Mangione will be detained

until his next hearing in January. He's currently behind bars at

the Metropolitan Detention Center in Brooklyn. That's the same facility where

Luigi Mangione hit with new charges that could carry death penalty

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Mangione faces federal charges, including murder, potentially resulting in the death penalty.

He was extradited from Pennsylvania to New York City to face charges.

He is accused of murdering United HealthCare CEO Brian Thompson.

Authorities stated that this act of terrorism will not be tolerated.

Mangione faces stalking and murder charges, potentially leading to the death penalty, in addition to existing state charges.

The federal complaint reveals new details about Mangione's efforts to track the victim.

Mangione extensively identified, surveilled, and tracked the victim's whereabouts before the murder.

The shooter was seen using a cell phone in the hours before the shooting.

Mangione's notebook contained pages related to the healthcare industry and statements about targeting insurance.

Mangione's Extradition and Court Appearance

Mangione waived his right to an extradition hearing in Pennsylvania.

He was transported by plane and helicopter to Lower Manhattan for his court appearance.

He has not yet entered a plea in either the state or federal case.

Mangione will remain detained until his next hearing in January at the Metropolitan Detention Center in Brooklyn.