The suspect in the killing of UnitedHealthcare’s CEO has been charged in Manhattan federal court on four counts, including murder, stalking and firearms offenses.

The federal criminal complaint against Luigi Mangione was unsealed two days after state prosecutors announced a grand jury indictment against him in the murder of executive Brian Thompson, who was shot dead on the streets of Manhattan.

The federal criminal complaint unsealed on Thursday charges Mangione with stalking – travel in interstate commerce, stalking – use of interstate facilities, murder through use of a firearm and a firearms offense.

The complaint alleges that Mangione was caught with evidence directly tying him to Thompson’s murder.

Mangione was found “to be in possession of a loaded 9mm pistol and silencer consistent with the weapon used to kill the victim, clothing that matched apparel that the shooter wore in the security camera videos, a notebook … several thousand dollars in cash … and a letter addressed ‘To the Feds’,” the complaint states.

It adds: “The notebook contained several handwritten pages that express hostility towards the health insurance industry and wealthy executives in particular.”

The complaint claims in an entry marked as “8/15” a passage describes how “the details are finally coming together” and “I’m glad – in a way – that I’ve procrastinated, bc it allowed me to learn more about [acronym for Company-1],” which the complaint states is United HealthCare.

The entry also states “the target is insurance” because “it checks every box” the complaint claims.

Another entry marked “10/22” allegedly states: “1.5 months. This investor conference is a true windfall … and – most importantly – the message becomes self evident.”

“And later in the Notebook it describes an intent to ‘wack’ the CEO of one of the insurance companies at its investor conference”, the complaint states.

The notebook is separate from a letter addressed “To the Feds”, the complaint says, in which Mangione allegedly wrote: “I wasn’t working with anyone” and “PS you can check serial numbers to verify this is all self-funded”.

“This was fairly trivial: Some elementary social engineering, basic CAD, a lot of patience,” the complaint alleges Mangione wrote in the letter.

The complaint also alleges Mangione traveled to New York for the “purpose of stalking and killing” Thompson and that while in the city, he “stalked and then shot and killed” the executive.

Prosecutors also have put together an alleged timeline of Mangione’s movements from 24 November up to and including 4 December, the date that the killing occurred, through hundreds of hours of security footage recordings.

They say that he arrived in New York City on 24 November on a bus that originated in Atlanta, Georgia. He then took a taxi to the area around the hotel where Thompson was shot, and stayed in the area for around an hour before taking another taxi to a hostel located on the Upper West Side of Manhattan.

At the hostel, they allege that he registered under the name Mark Rosario and provided a fake New Jersey ID.

On the day of the murder, the suspect allegedly left the hostel at around 5.35am in the morning, and rode an electric bike down to a location near the Midtown hotel, wearing a gray backpack.

After arriving in the area, Mangione allegedly walked around and at one point purchased items from a nearby coffee shop and then returned to a bench in the vicinity of the hotel.

At around 6.45am the suspect allegedly saw and approached Thompson and shot him multiple times, and then fled on foot, then electric bike, then taxi, dropping his backpack on the way.

Earlier on Thursday, Mangione appeared in court in Pennsylvania, where he was arrested last week after five days on the run, and agreed to be extradited to New York.

He waived a preliminary hearing on the Pennsylvania charges in exchange for the prosecutor giving him a 20-page investigative report from the Altoona police department.

Mangione arrived in New York later on Thursday in a police helicopter and was then transferred via a “perp walk” into a waiting vehicle. Mangione walked slowly, flanked by law enforcement, as he wore an orange jumpsuit and had his hands handcuffed in front of him.

The 26-year-old Ivy League graduate is accused of ambushing and shooting Brian Thompson on 4 December outside a Manhattan hotel, where the head of the United States’ largest health insurer 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 on 9 December while eating breakfast at a McDonald’s in Altoona, Pennsylvania.

Earlier this week, Mangione was indicted by a New York grand jury and charged with state murder charges including first-degree murder, two counts of murder in the second degree, along with other weapon and forgery charges.

The New York state case against Mangione will happen alongside the federal case against him.

In court in Manhattan, Mangione, now wearing a blue sweater and beige slacks, with his ankles in chains, made an initial appearance on the federal charges before US magistrate judge Katharine Parker. He spoke briefly to confirm to Parker that he understood his rights and the fresh federal charges.

Mangione’s lawyer told the court that he would not seek to be released on bail and Parker ordered that he remain in custody. He will be asked to enter a plea at a future hearing.

“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,” Mangione’s lawyer Karen Friedman Agnifilo said in a statement before Thursday’s hearing.

She added: “We are ready to fight these charges in whatever court they are brought.”

Mangione is also facing separate charges in Pennsylvania for carrying a gun without a license, forgery, falsely identifying himself to the authorities and possessing “instruments of crime”.

The Associated Press and Reuters contributed reporting