Luigi Mangione traveled from Georgia to allegedly stalk and kill UnitedHealthcare CEO Brian Thompson and said he targeted the health care industry because "it checked every box" -- one of a number of entries in a notebook in which the suspect discussed the plot in the weeks before the brazen crime, according to a federal criminal complaint.
Mangione was hit with four federal charges Thursday, including stalking, a firearms offense involving a silencer and murder through use of a firearm, a charge that makes him eligible for the death penalty.
The federal complaint contains previously unreleased excerpts from the notebook that police said they seized from Mangione. Authorities said the writings "express hostility towards the health insurance industry and wealthy executives in particular."
A special edition of "20/20" airing Dec. 19 at 10 p.m. ET on ABC looks at the murder of UnitedHealthcare CEO Brian Thompson and the manhunt that led to the arrest of Luigi Mangione, who went from the Ivy League to alleged killer.
According to the complaint, an entry marked Aug. 15, 2024, said "the details are finally coming together," and, "I'm glad -- in a way -- that I've procrastinated, bc [because] it allowed me to learn more about [acronym for Company-1]."
In an entry marked Oct. 22, 2024, the writings said, "1.5 months. This investor conference is a true windfall ... and -- most importantly -- the message becomes self evident."
Later on in the entry, the pages describe an intent to "wack" the CEO of one of the insurance companies at its investor conference, the complaint said.
Mangione waived extradition on Thursday morning and was transported via plane and helicopter from Pennsylvania to New York.
New York City Mayor Eric Adams and NYPD Police Commissioner Jessica Tisch were waiting when Mangione arrived in Manhattan.
Mangione made his initial appearance in federal court in lower Manhattan on Thursday afternoon and answered "yes" to several questions by the judge. Mangione, wearing chinos, a white shirt and black quarter-zip sweater, appeared docile and stone-faced at the defense table. He did not enter a plea.
Mangione's New York lawyer, Karen Friedman Agnifilo, said her client was prepared to appear in state court and complained the federal charges were sprung on them.
"This is a highly unusual situation we find ourselves in," Agnifilo said. "I have never seen anything like that."
MORE: What we know about Luigi Mangione, Ivy League grad charged in CEO's murderShe said the theories of the two cases appear to be in conflict, noting the state case accused Mangione of terrorizing a group of people while the federal case accused him of stalking an individual.
The judge told the parties to confer.
Mangione’s next court date is Jan. 18.
Mangione will be remanded into custody at MDC Brooklyn, the same federal lockup where Sean "Diddy" Combs is currently jailed.
The federal charges could make Mangione eligible for the death penalty. He faces a maximum sentence of life in prison without parole if convicted of the state charges.
Danielle Filson, a spokesperson for Manhattan District Attorney Alvin Bragg, said this week that "the state case will proceed in parallel with any federal case."
Mangione first appeared in court in Blair County, Pennsylvania, on Thursday morning and agreed to be extradited to New York.
Mangione stood as the judge read him his rights. The Ivy League graduate answered "yes" when asked if he understood and answered "yes" when asked if he wanted to waive extradition.
Spectators gathered outside the Blair County courthouse as Mangione was taken inside.
One person held a sign reading "Deny, Defend, Depose," echoing the words written on shell casings and a bullet at the murder scene.
Adam Giesseman, who had a sign that said "Free Luigi" and "Murder for Profit is Terrorism," told ABC News, "Our country is broken."
Another waiting spectator, who only gave her first name, Natalie, voiced frustration that the insurance system is "set up for profit over people's health."
"It's unfortunate that this happened, and I'm not glorifying it in any way -- but it's brought attention to the issue that affects all Americans," she said.
MORE: UnitedHealthcare CEO shooting suspect's timeline before, during, after the brazen murderMangione, 26, is accused of gunning down Thompson outside a Hilton hotel on Dec. 4 as the UnitedHealthcare CEO headed to an investors conference. Prosecutors alleged Mangione waited nearly an hour for Thompson to arrive.
A Manhattan grand jury upgraded charges against Mangione to include first-degree murder in furtherance of terrorism, prosecutors announced Tuesday.
The killing in the heart of Midtown Manhattan was "intended to evoke terror," Bragg said.
In New York, Mangione is also charged with two counts of second-degree murder, one of which is charged as killing as an act of terrorism; two counts of criminal possession of a weapon in the second degree; four counts of criminal possession of a weapon in the third degree; one count of criminal possession of a weapon in the fourth degree; and one count of criminal possession of a forged instrument in the second degree.
In Pennsylvania, where Mangione was arrested on Dec. 9 after nearly a week on the run, he faces charges including allegedly possessing an untraceable ghost gun. Mangione had a 9 mm handgun with a 3D-printed receiver, a homemade silencer, two ammunition magazines and live cartridges when apprehended, prosecutors said.
Mangione's case in Pennsylvania will be kept active; at the conclusion of his trial in New York, prosecutors would determine how to proceed, Blair County District Attorney Peter Weeks said on Thursday.
Mangione's next hearing in Pennsylvania is scheduled for Feb. 24. This hearing may get postponed or be conducted as a remote Zoom appearance given the impracticality of returning Mangione to Pennsylvania for an in-person hearing, Weeks said.