By Dalia Faheid, Michelle Watson, Bonney Kapp, John Miller and Dakin Andone, CNN

(CNN) — [Breaking news update, published at 2:17 p.m. ET]

The gun CEO killing suspect Luigi Mangione had when he was arrested this week in Pennsylvania matches shell casings found at the crime scene last week in Midtown Manhattan, the New York Police Department commissioner said Wednesday.

“First we got the gun in question back from Pennsylvania. It’s now at the NYPD crime lab,” Commissioner Jessica Tisch said at an event unrelated to the homicide investigation. “We were able to match that gun to the three shell casings that we found in Midtown at the scene of the homicide.”

[Original story, last published at 12:38 p.m. ET]

Fingerprints found at the scene of the assassination of UnitedHealthcare’s CEO match those of suspect Luigi Mangione, two law enforcement officials briefed on the matter told CNN on Wednesday, as authorities continue to investigate the motive for the killing.

This marks the first positive forensic match tying Mangione directly to the scene where Brian Thompson was gunned down just over a week ago outside a Midtown Manhattan hotel.

CNN has reached out to Mangione’s attorney for comment on the fingerprint match.

The development comes as authorities dig into Mangione, who remains in custody in Pennsylvania on gun-related charges as he fights extradition to New York, where he’s charged with murder.

Since his arrest Monday thanks to a tipster at a McDonald’s, the 26-year-old’s background is starting to come into focus. The privileged scion of a well-to-do family, high school valedictorian and Ivy League graduate vanished from view of his loved ones in recent months, only to emerge as the suspect in a high-profile killing potentially fueled by his struggle with a painful back injury.

The killing of Thompson – a husband and father of two – has laid bare many Americans’ fury toward the health care industry, with Mangione garnering sympathy online and offers to pay his legal bills. It’s also struck fear in C-suites across the country, as a New York Police Department intelligence report obtained by CNN warns online rhetoric could “signal an elevated threat facing executives in the near-term …”

Mangione’s lawyer has denied his client’s involvement in the killing in New York and anticipates he will plead not guilty there to the murder charge, among other counts. Mangione also plans to plead not guilty to Pennsylvania charges related to a gun and fake ID police found when they arrested him in Altoona, attorney Thomas Dickey said.

“I haven’t seen any evidence that they have the right guy,” Dickey told CNN’s Kaitlan Collins on “The Source.” Dickey has not seen the evidence, including writings police said were in Mangione’s possession at the time of his arrest, the lawyer reiterated Wednesday on ABC’s “Good Morning America.”

In some of Mangione’s writings, he referenced pain from a back injury he got in July 2023, New York Police Chief of Detectives Joseph Kenny told Fox News on Tuesday. Investigators are looking into an insurance claim for the injury.

“Some of the writings that he had, he was discussing the difficulty of sustaining that injury,” Kenny said. “So, we’re looking into whether or not the insurance industry either denied a claim from him or didn’t help him out to the fullest extent.”

Mangione was denied bail at an extradition hearing Tuesday afternoon at the Blair County Courthouse in Pennsylvania.

As he entered the courthouse, shackled at the hands and feet and wearing an orange prison jumpsuit with DOC emblazoned on the back, he yelled, in part, “It’s completely out of touch and an insult to the intelligence of the American people. It’s lived experience.”

Investigators detail gun, silencer and fake ID

New York prosecutors charged Mangione with one count of murder, two counts of second-degree criminal possession of a weapon, one count of second-degree possession of a forged document, and one count of third-degree criminal possession of a weapon, online court documents show.

Mangione is the person seen in surveillance video fatally shooting Thompson outside a Hilton hotel en route to his company’s annual investor conference, ?officials assert, citing charging documents in which Detective Yousef Demes of the Midtown North Detective Squad outlines evidence, including that the man seen in surveillance footage from a New York hostel is wearing the same clothing.

After arresting Mangione in the Altoona McDonald’s, police found “a black 3D-printed pistol and a black silencer” that was also 3D printed, according to the criminal complaint. While being taken into custody, Mangione also presented a forged New Jersey ID with the name Mark Rosario, which matched the ID the man at the hostel used, Demes wrote.

Suspect appeared to view targeted killing as a ‘symbolic takedown’

The suspect appeared to be driven by anger against the health insurance industry and against “corporate greed” as a whole, according to an NYPD intelligence report obtained Tuesday by CNN.

“He appeared to view the targeted killing of the company’s highest-ranking representative as a symbolic takedown and a direct challenge to its alleged corruption and ‘power games,’ asserting in his note he is the ‘first to face it with such brutal honesty,’” says the NYPD assessment, which was based on Mangione’s “manifesto” and social media.

Along with a three-page handwritten “claim of responsibility” found on Mangione when he was taken into custody, investigators are looking at the suspect’s writing in a spiral notebook, a law enforcement source briefed on the matter told CNN.

It included to-do lists to facilitate a killing, as well as notes justifying those plans, the source said. In one notebook passage, Mangione wrote about the late Ted Kaczynski, the so-called Unabomber who justified a deadly bombing campaign as an effort to protect against the onslaught of technology and exploitation. Mangione had written about the Unabomber in online posts as well.

Mangione knew UnitedHealthcare was holding an investors’ conference around the time Thompson was shot and killed — and the suspect mentioned in writings he would be going to the conference site, the NYPD’s Kenny told Fox News on Tuesday.

In the notebook passage, Mangione concludes using a bomb against his intended victim “could kill innocents” and shooting would be more targeted, musing what could be better than “to kill the CEO at his own bean counting conference,” a law enforcement official briefed on the matter told CNN.

The three-page document did not include specific threats but indicated “ill will towards corporate America,” Kenny said.

Why Mangione may be fighting extradition

With Mangione fighting extradition, a Pennsylvania court has given him 14 days to file for writ of habeas corpus – putting the burden of proof on those detaining the person to justify the detention – and a hearing will be scheduled if he does.

Pennsylvania prosecutors have 30 days to get a governor’s warrant, which New York Gov. Kathy Hochul said she will work with prosecutors to sign and Pennsylvania Gov. Josh Shapiro “is prepared to sign and process … promptly as soon as it is received.” Blair County District Attorney Peter Weeks said his office is prepared “to do what’s necessary” to get Mangione back to New York.

There could be several reasons Mangione is fighting his extradition, said Karen Agnifilo, a CNN legal analyst and defense attorney. It would give him more time to think about his defense, demand prosecutors present more evidence at his next hearing or try to get bail in Pennsylvania, which is unlikely.

Indeed, it could take up to two months before authorities could bring Mangione back to New York after the governor’s warrant is obtained, said Agnifilo, who previously worked at the Manhattan District Attorney’s Office.

Most criminal defendants facing prosecution on more serious charges in another state waive their right to extradition, but in murder cases like Mangione’s, “there’s no chance he’s going to be let out, so he’s fighting extradition,” she said.

“Eight or 9 out of 10 times, defendants waive extradition because they realize this is so perfunctory, it’s so easy, and most of them don’t want to languish in detention in the other state because you don’t even get to fight your case yet,” Agnifilo said.

Pennsylvania state Judge Dave Consiglio denied Mangione bail related to both state dockets, saying he would remain at the Huntingdon State Correctional Institution.

CNN’s Steve Almasy, Sara Smart, Gloria Pazmino, Amanda Musa, Celina Tebor, Elizabeth Hartfield, Elise Hammond, Emma Tucker, Jordan Valinsky, Danny Freeman and Kara Scannell contributed to this report.

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