He cut off some loved ones for months. Now, suspect Luigi Mangione faces mounting evidence in health care CEO’s killing

By Karina Tsui, Steve Almasy, Andy Rose, John Miller, Brynn Gingras and Kara Scannell, CNN

Marked shell casings from the assassination scene match the gun found on the suspect. His fingerprints match some key items investigators found nearby. And he was arrested this week - after going silent from his mom and friends for months - with a fake ID and a handwritten "claim of responsibility" referencing the crime site.

These details and others, shared by law enforcement and people who know suspect Luigi Mangione, have been mounting since last week's daylight killing of UnitedHealthcare CEO Brian Thompson on a busy sidewalk in Midtown Manhattan.

Authorities have executed as many as three search warrants in New York as part of the investigation into Thompson's killing, sources tell CNN.

A law enforcement source with knowledge of the investigation tells CNN at least two of the warrants include the backpack found in Central Park and the burner phone found along the getaway route police believe Mangione took from the shooting scene. Investigators also searched the hostel where suspected killer Mangione stayed the night before the shooting and the hotel room where Thompson was staying while in New York.

After a five-day, multi-state manhunt that leaned heavily on surveillance images and pleas for the public's help, Mangione, 26, is now charged in the case with murder after a tip led to his arrest Monday at a McDonald's nearly 200 miles from where the brazen homicide unfolded.

Prosecutors from the Manhattan District Attorney's Office have begun presenting evidence to a grand jury in the case against Mangione, sources told ABC News.

Mangione was charged in a felony arrest warrant earlier this week. The presentation of evidence to a grand jury is the next procedural step in obtaining an indictment.

Mangione's lawyer has denied his client's involvement in the December 4 killing and anticipates he will plead not guilty to the murder and other charges in New York, as well as to charges related to the 3D-printed gun and fake ID in Pennsylvania, where he was caught and is being held without bond.

Defense attorney Thomas Dickey on Wednesday also dismissed the ballistics and fingerprint evidence revealed publicly hours earlier, saying he wants to examine it himself.

"Those two sciences, in and of themselves, have come under some criticism in the past, relative to their credibility, their truthfulness, their accuracy, however you want to do it," Dickey said on CNN's "Erin Burnett OutFront."

"As lawyers, we need to see it. We need to see: How did they collect it? How much of it? And then we would have our experts … take a look at that, and then we would challenge its admissibility and challenge the accuracy of those results."

Still, New York's governor expects a murder indictment "to be issued any day now, and the second that happens, I'm issuing a warrant for extradition."

"It feels like the evidence is very compelling," Gov. Kathy Hochul told MSNBC's Morning Joe on Thursday. "I trust the DA here in Manhattan to make sure that he puts forth an indictment that is going to be iron-clad."

Meanwhile, Hochul is unimpressed by the folk hero status Mangione has attained on social media as the killing of Thompson - a husband and father of two - has laid bare many Americans' fury toward the health care industry.

Mangione appears to have been driven by anger against the industry and "corporate greed" as a whole, states a New York Police Department intelligence report that also warns online rhetoric could "signal an elevated threat facing executives in the near-term."

"That horrific attack occurred on our streets," Hochul said Thursday. "And the people of our city deserve to have that sense of calm that this perpetrator has been caught, and he will be never seeing the late of day again if there is justice."

"You cannot assassinate an individual on the streets of New York - not now, not ever."

Suspect hadn't spoken to mother since July

Until he was found Monday in Altoona, Pennsylvania, Mangione had gone quiet from at least a few people who appear to have been close with him. The scion of a wealthy Baltimore family who was a high school valedictorian and an Ivy League graduate, he had maintained an active social media presence for years, posting smiling photos from his travels, sharing his weightlifting routine and discussing health challenges he faced.

Mangione's mother had reported him missing November 18 - two weeks before Thompson's killing - a law enforcement official briefed on the investigation told CNN on Wednesday. She called police in San Francisco, where she knew her son had been living, and told authorities she'd called his phone repeatedly to find the voicemail full and not taking any more messages.

Mangione's mom had no reason to believe her son was a danger to himself or others, she told the San Francisco Police Department, but she hadn't actually spoken with him since July 1, the official said. He had worked remotely at TrueCar, she also said, where the phone was disconnected and the offices closed, the official added.

It also doesn't appear Mangione had posted anything since midsummer to social media, where posts addressed to his X account suggest some of his friends have been trying to get in touch with him.

In July, a user tweeted at Mangione, "I haven't heard from you in months," urging him to let him know if Mangione could honour the "commitments" he had made for the user's wedding. In late November, just weeks before the shooting, another user posted at Mangione, "thinking of you and prayers everyday in your name. Know you are missed and loved".

As Mangione entered a Pennsylvania courthouse this week, shackled at the hands and feet and wearing an orange prison jumpsuit, he yelled, in part, "It's completely out of touch and an insult to the intelligence of the American people. It's lived experience."

"He's irritated, agitated about what's happening to him and what he's being accused of," Dickey told CNN of Mangione's outburst and struggle with police.

"He never had any legal representation until he walked into that building yesterday. And I talked to him … look at the difference between when he went in and when he came out … now he has a spokesperson and someone that's going to fight for him."

Suspect linked to fingerprints and gun

Police in New York on Wednesday publicly revealed the first positive forensic match and direct physical evidence tying Mangione to Thompson's killing, law enforcement officials told CNN.

"We got the gun in question back from Pennsylvania. It's now at the NYPD crime lab," NYPD Commissioner Jessica Tisch said. "We were able to match that gun to the three shell casings that we found in Midtown at the scene of the homicide."

A 3D-printed gun was in Mangione's possession when he was arrested Monday, police have said.

The three 9 mm shell casings had the words "delay," "deny" and "depose" written on them, one word per bullet, law enforcement sources have told CNN. Police have been looking into whether those words, which match the title of a 2010 book critiquing the insurance industry, may point to a motive in the killing.

Authorities also had been probing DNA material and a partial fingerprint from a discarded Starbucks water bottle and an energy bar wrapper surveillance images showed the suspect buying about 30 minutes before the shooting. Mangione's fingerprints were confirmed as a match, Tisch said

Along with the prints and ballistics, investigators have been examining writings police have said Mangione had upon arrest, including a three-page handwritten "claim of responsibility." It did not include specific threats but indicated "ill will towards corporate America," New York Police Chief of Detectives Joseph Kenny has said.

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

In some writings, he referenced pain from a back injury he got in July 2023, Kenny added. 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."

Investigators also 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.

In a 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.

"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 writings and social media.

CNN's Dalia Faheid, Michelle Watson, Bonney Kapp, Dakine Andone, Sara Smart, Gloria Pazmino, Amanda Musa, Celina Tebor, Elise Hammond, Emma Tucker, Jordan Valinsky, Danny Freeman and Kara Scannell contributed to this report.

- CNN