Police in San Francisco identified UnitedHealthcare CEO Brian Thompson's alleged killer, Luigi Mangione, and alerted the FBI four days before his high-profile arrest, a new report says.

An officer tipped off the feds after recognizing the 26-year-old's face in surveillance images put out by the NYPD after Thompson was gunned down last week, sources told the San Francisco Chronicle.

Mangione's face was known to cops in California because he'd been reported missing by his family just weeks earlier on Nov. 18, the sources added.

When Mangione was eventually nabbed at a Pennsylvania McDonald's after a five day manhunt on Monday, authorities had said the alleged assassin identity wasn't on their radar.

It wasn't immediately clear if the FBI ever received the tip from cops, or if they acted on it.

Luigi Mangione, the Ivy League graduate accused of gunning down UnitedHealthcare CEO Brian Thompson, was never a client of the medical insurance giant, a senior NYPD official revealed Thursday. 

Chief of Detective Joseph Kenny told NBC that he suspects the alleged 26-year-old gunman may have targeted Thompson due to the size and influence of the health insurance company.

Kenny said investigators found evidence that Mangione was aware UnitedHealthcare was holding its annual investor conference at a Manhattan hotel the day of the cold-blooded slaying.

When Mangione was arrested at a Pennsylvania McDonald's on Monday, he was in possession of a manifesto-type note that mentioned UnitedHealthcare, sources have previously told The Post.

“We have no indication that he was ever a client of UnitedHealthcare, but he does make mention that it is the fifth largest corporation in America, which would make it the largest healthcare organization in America,” Kenny told the outlet. 

“So that’s possibly why he targeted that company.”

Mangione is accused of fatally shooting Thompson as the 50-year-old CEO walked to the Hilton hotel on Sixth Avenue, where UnitedHealthcare’s parent company, UnitedHealth Group, was holding its annual investor conference on Dec. 4.

While investigators have not characterized the killing of UnitedHealthcare CEO Brian Thompson as a terror attack, the murder's "impact is similar to that of a domestic terror attack," an NYPD counterterrorism official said.

"I think regardless of what the courts determine the motivation to be, the impact is similar to that of a domestic terror attack, and that is already being reflected in this just torrent of online vitriol that we've been in the midst of since last Wednesday, and the lionization of the alleged perpetrator of the murder as a hero," Rebecca Weiner, deputy commissioner of the NYPD's Counterterrorism Bureau, said during a panel discussion Wednesday in Washington, DC, about the future of US counterterrorism policy.

What role did tech play in the ongoing case against Luigi #Mangione, suspected for murdering #UnitedHealthCare CEO?

“We can't do any kind of crime fighting without video canvases and cameras, there's 70,000 cameras that are networked,” explains @NYPDCT’s Rebecca Weiner.

"This… pic.twitter.com/0oxhhGZ5nT

— Atlantic Council Middle East Initiatives (@ACMideast) December 11, 2024

Weiner, answering a question about the role of tech in the stunning targeted killing, warned that it "has all the hallmarks" of something that could prompt copycats.

"So when we are concerned about terrorism, it is in part because of outsized impact of a particular act of violence," she said. "This one has all the hallmarks of something that is going to inspire and contribute to a contagion effect given all of those factors."

Weiner also gave insight into how the NYPD is "going to deal with" the "wanted" posters with names and faces of Thompson and executives of other health insurance companies that have cropped up across the city this week.

"This is going to take on a counterterrorism footprint, regardless of the underlying motivations of the individual," she said.

New York Gov. Kathy Hochul says accused killer Luigi Mangione will be indicted “any day now” for the shooting of UnitedHealthcare CEO Brian Thompson. 

"I trust the DA here in Manhattan to make sure that he puts forth an indictment that is going to be ironclad,” Hochul said on MSNBC’s "Morning Joe." 

Hochul said she trusts Manhattan District Attorney Alvin Bragg to put together a strong case against Mangione, 26, adding that she will be issuing a warrant extradition the moment the indictment goes through. 

"I want to get him back here in the state of New York and run him through our criminal justice system, because that horrific attack occurred on our streets, and the people of our city deserve to have that sense of calm that this perpetrator has been caught and he will never see the light of day again if there is justice.

"You cannot assassinate an individual on the streets of New York. Not now. Not ever," she said. 

Bragg said Thursday morning that he was confident in his office’s ability to secure an indictment as it presents mounting evidence against Mangione to a grand jury. 

"This is obviously a profound, profoundly disturbing, as we've alleged, murder," Bragg told ABC 7. "We would not charge the person if we didn't think it was the person and we're prepared to go forward."

Inmates at the Pennsylvania prison where Luigi Mangione is being held conducted a wild interview with a TV reporter outside, screaming answers out the windows and flickering the lights to signal yes or no.

NewsNation journalist Alex Caprariello was reporting on Mangione's conditions at the State Correctional Institution in Huntington, Pennsylvania, Wednesday when inmates, who were watching him on TV, yelled out, "Luigi's conditions suck."

Caprariello returned to the prison at 10 p.m. for Ashleigh Banfield, when the inmates watched the program on TV and answered questions Banfield posed from her studio desk.

The prisoners screamed "No" when asked if Mangione had a television in his cell.

"This is the strangest interview I've ever conducted," Banfield said.

After Banfield read the prison's menu for the day and asked the inmates if the food was good, she was met with a chorus of prisoners screaming that it was "terrible" and "B.S."

Accused CEO killer Luigi Mangione was turned away from a hotel in Altoona, Pa., the same morning he was busted at a McDonald's just minutes down the road.

Hotel clerk John Kuklis said the alleged assassin was acting "somewhat circumspect" when he entered the Horseshoe Curve Lodge early Monday looking for a room.

“He basically just walked in kind of cagey, just looking around, making sure he wasn’t being watched, asked if he could get a room here,” Kuklis told ABC News.

With no clean rooms available, Kuklis told the accused gunman to leave and come back in the afternoon after Mangione asked if he could hang out in the hotel lobby until a room was ready, the clerk said.

"He said, 'OK.' And he turned around and just left. Didn't say anything. Never took his mask down," he added, the outlet reported.

Mangione wound up hanging out at the fast food joint -- a roughly 17-minute walk from the hotel -- instead, before a customer recognized him.

He had been wearing a face mask at the eatery but lowered it at times to munch on hash browns when he was recognized from surveillance footage released of the UnitedHealthcare CEO Brian Thompson shooting suspect. The customer who spotted him alerted an employee, who called the police.

A bag of bullets found by a person walking their dog in Central Park on Tuesday has been ruled out as being connected to the fatal shooting of United Healthcare CEO Brian Thompson, law enforcement sources told The Post.

The bullets in the Ziploc bag were of a different caliber than those used in Thompson’s slaying, sources said Wednesday.

Investigators are probing whether Luigi Mangione's back injury was the alleged motive in the cold-blooded killing of UnitedHealthcare CEO Brian Thompson, police said.

"A possible motive that we are also looking into is that he suffered an accident that caused him to visit an emergency room back on July 4 of 2023," an NYPD official said Wednesday.

"He posted X-rays of numerous screws being inserted into his spine -- and [in] some of the writings, he was discussing the difficulty of sustaining that injury."

The 26-year-old accused killer had "animus toward the health care industry," the official added.

Cops are still “vetting” the hundreds of tips they received in the assassination of UnitedHealthcare CEO Brian Thompson — as it remains unclear whether suspected killer Luigi Mangione’s family recognized him while he was on the run.

NYPD Deputy Commissioner of Operations Kaz Daughtry was pressed on MSNBC’s “Morning Joe” Wednesday about whether Mangione’s relatives — part of a prominent Baltimore, Md., clan — had contacted authorities to identify him.

“We’re still vetting each one of those tips. But thank God for the customer that was in the McDonalds,” Daughtry said, referring to the tipster who called the cops after Mangione was spotted chomping on hashbrowns at a fast food joint in Altoona, Pennsylvania Monday.

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A person walking their dog in Central Park on Tuesday found a ziplock bag filled with bullets -- but cops analyzed them and ruled them out as being linked to the murder of UnitedHealth CEO killer Luigi Mangione, law enforcement sources said. 

The dog walker said they were strolling near East 81st and 85th Street when they spotted the bag in the bushes and saw shell casings inside, Fox 5 reports. 

Police previously found a backpack believed to belong to murder suspect Luigi Mangione in the park.

The suspect made his escape by riding an e-bike through the green space in the aftermath of Thompson's Dec. 4 shooting in Midtown.

The bullets in the plastic bag, however, were of a different caliber than those used in Thompson's slaying, sources told The Post Wednesday, and cops have ruled them out as being related.

Luigi Mangione's middle school teacher says she can't believe her former student went on to allegedly commit the heinous on-the-street execution of UnitedHealthcare CEO Brian Thompson.

"It just doesn’t make any sense," Gilman School teacher Liz Sesler-Beckman told WICU of Erie, Pennsylvania.

Sesler-Beckman said that Mangione was never one of the students she worried about, and that the person she sees on TV is unrecognizable from the young boy she once knew.

"It’s like a cognitive dissonance between the person that we all knew and the person who would commit such a heinous crime," she added.

“I am devastated for the Gilman community, his family and of course for the victim’s family. It’s just unthinkable that he would resort to that kind of violence."

The suspect in the brutal murder of UnitedHealthcare CEO Brian Thompson visited Japan multiple times this year and told locals he "loves Japanese culture" before going on to bash the country months later, NBC news reported.

Luigi Mangione struck up a conversation with poker player Obara Jun at a local restaurant, who described the future suspected gunman as "very friendly."

“[he] told me that he loves Japan and Japanese culture,” he said.

Obara described Mangione as "very smart" and "friendly" and claimed the two followed each other on X before going their separate ways.

Mangione would later email Substack author Gurwinder Bhogal that Japan was "peak NPC-ville" and its citizens display a "scary lack of free will." NPC is a video gaming term which stands for "non-playable character" and is often used as an insult meant to convey that a person isn't thinking for himself.

The email went on to relate a story in which Mangione claims he witnessed a Japanese police officer refuse to cross the street to help a man who was having a seizure because the light was red.