Investigators believe that Luigi Mangione, known as the ‘CEO assassin,’ did not work by himself, and there are three important pieces of evidence to support this.

Top crime investigators believe that the suspected UnitedHealthcare CEO shooter executed the cold-blooded murder with the assistance of an accomplice, as revealed by DailyMail.com.

The nation has been captivated by the case of Ivy League graduate Luigi Mangione, who has been dubbed the ‘heartthrob’ and was identified by police as the perpetrator in the fatal shooting of Brian Thompson in New York City earlier this month.

Mangione, aged 26, was initially charged with murder in the slaying that occurred on December 4. However, on Tuesday, he faced an additional charge of murder as an act of terrorism. His lawyer confirmed that he will be returning to New York on Thursday after agreeing to extradition.

In a 262-word manifesto reportedly found on Mangione when he was arrested, the suspect said he acted alone.

But two leaders in the investigative field who have analyzed the case have now told DailyMail.com that some key details are being ignored – and that those clues point to at least one accomplice to the alleged murderer.

Brian O’Shea worked for 11 years in US Army intelligence, another decade as a contractor for US intelligence agencies, and then ran a high-end private intelligence firm until 2022. His investigations for clients have included several murder cases.

O’Shea says the coincidence of the shooter arriving within five minutes of Thompson emerging from his hotel, suspicious behavior by others on CCTV, and conflicting witness statements, all suggest the killer knew exactly when to pounce thanks to help from at least one other person.

A second industry leader in private intelligence for celebrities and CEOs spoke to DailyMail.com on condition of anonymity due to being close to the case.

This second top security expert also pointed to CCTV footage of the assassin talking on the phone to an as-yet-unidentified contact while walking to the Hilton Midtown 15 minutes before the murder took place.

These top PIs are asking: could that call have been from an accomplice monitoring the movements of the UnitedHealthcare CEO?

‘The odds of you getting somewhere right when your mark is getting there are next to impossible,’ O’Shea told DailyMail.com in an exclusive interview.

‘I’ve done probably over 2,000 hours of surveillance, and probably half of those in New York City. It takes a long time to get to the right place at the right time.

‘The best way to be at the right place at the right time is to have a team, have intelligence on the movement of the target, and to have that team and yourself sit there for a long time until that person moves.’

‘All public figure attacks have what we call a staging location,’ said the second expert close to the case.

‘That is the location from which the actual attack is mounted. Nearly every public figure attack is over in less than five seconds. But the staging location might be occupied for hours.’

O’Shea, host of the podcast Investigate Everything, has been going through the timeline of events and security camera footage surrounding the murder with a fine tooth comb, looking for clues.

The suspect, believed to be Mangione, was seen arriving at the New York Hilton Midtown hotel at 5:41am on December 4, police sources told the New York Times, adding that he paced up and down West 54th Street before leaving.

Police said they believed he traveled there that morning by bicycle from the Upper West Side hostel he was staying in.

However, CCTV obtained by the Washington Post appears to show the same person exiting the 57th Street Subway at 6:15am. It is unclear why the shooter would have gone back to the subway after arriving at his target’s location.

At 6:17am, the shooter was caught on camera at a nearby Starbucks on West 56th, located between the Subway station and the Hilton. The top half of his face above his mask seems to match Mangione.

At 6:20am a security camera outside Stage Star Deli on West 55th Street filmed what appears to be the shooter walking west towards the Hilton.

O’Shea expressed consternation that the assassin would leave his intended kill-spot just a few minutes before the hit.

‘With a three-minute window, which killer is going to stop at Starbucks for a Kind bar and a bottle of water? It just doesn’t make any sense,’ he said.

But the next piece of footage in the timeline could be the reason the killer knew when to return.

The Times obtained surveillance footage they say is of the suspect walking about 175 feet from where Thompson was shot, at 6:30am.

The shooter appears to be on the phone in the video, raising the prospect that an accomplice monitoring Thompson’s movements called him to say that the CEO would shortly be leaving his hotel, the five-star Marriott across the street from the Hilton.

‘If it were me doing surveillance of this sort, I’d be paying off a door guard or concierge. Like, “Hey man, I’m really trying to see what’s going on with this guy. Can you help me out?”‘ said O’Shea.

‘It just seems like a team that was doing good surveillance and reporting to their client.’

At 6:39am, just five minutes before Thompson emerged from his hotel, the man police believe is Mangione arrived at the Hilton Midtown and took his position between two parked cars, ready to attack.

However, a witness interviewed by media shortly after the shooting said that they saw the shooter loitering on the street corner ‘all night’ – another piece of evidence that O’Shea says raises the prospect of multiple individuals being involved.

‘This guy, he was here on the corner all night. The guy who shot the guy. He was standing here on this corner,’ the witness told Fox News.

Examining the timeline of events, both security experts highlighted another intriguing wrinkle.

According to police, Mangione traveled on a Greyhound bus originating in Atlanta, Georgia, arriving in New York City on November 24.

According to a CBS report, police sources say he immediately took a cab to the Hilton Midtown and spent 30 minutes walking the streets around it, leaving to check in at his Upper West Side hostel around 11pm.

But the date and Hilton location for the UnitedHealthcare investor conference, where Thompson was set to speak, wasn’t publicly announced until two days later on November 26.

How did the shooter know where to go? 

The top PI source close to the case said it is ‘a very good question’.

‘I continue to be interested in learning how Luigi could possibly have learned the details of the meet date and location in advance,’ the source said.

‘The assassin needs to know either where his target is starting off for the day or where he is ending up for the day.

‘It is possible that someone who intimately knew the schedule for the CEO provided information to the shooter, or to someone else, who provided it to the shooter.’

Mangione allegedly claimed he acted alone, in a 262-word manifesto found on him according to police.

‘To save you a lengthy investigation, I state plainly that I wasn’t working with anyone,’ the handwritten document said, according to a transcription published by journalist Ken Klippenstein on his Substack on December 10.

‘This was fairly trivial: some elementary social engineering, basic CAD [computer aided design], a lot of patience.’

Social engineering, according to a Department of Defense definition, is ‘the art of manipulating people into performing actions or divulging confidential information, rather than by breaking in or using technical cracking techniques.’

If the manifesto is authentic, Mangione may have been hinting at having duped United Health staff, or people close to Thompson, to give up his location ahead of company announcements.

O’Shea said he was also interested in the driver of an SUV parked outside the Hilton right next to the murder location.

‘Right as Brian Thompson steps into view of the two dome cameras, that SUV steps on its brake lights for no apparent reason and holds them there,’ the military intelligence veteran said.

He added that this is a common method for a PI surveillance team in a car to discreetly notify each other of a nearby target’s movements.

‘The way we would mark the target is by stepping on the brake lights in a situation like this,’ he said.

And if the driver was not involved, O’Shea said, he still wants to see his dashcam footage.

‘Those are private drivers. They all have dash cameras. The suspect trotted right in front of the SUV still stepping on its brake lights.

‘If we could see the dash cam footage of when he passed right in front of that SUV, we’d have a clear view of his face.’

O’Shea said the unanswered questions and potential inconsistencies are fodder for Mangione’s defense attorney, who will be trying to pick apart New York District Attorney Alvin Bragg’s evidence for Mangione’s first-degree murder charge.

‘I’ve worked for a lot of defense counsels. I’ve worked several murder investigations,’ he said. ‘They’re up against a lot, especially when they’re up against the government.’

One inconsistency O’Shea said Mangione’s lawyer Thomas Dickey will be probing, is the timestamp on crucial camera footage.

He pointed out that the CCTV obtained by the New York Times of the shooter on the phone and walking close to the crime scene around 6:30am, actually says 7:29am on the camera watermark in the top left corner.

The Times cropped out the timestamp when they published the footage, but ABC left it in their published story.

However, security camera owners will often forget to reset the system’s clock to adjust for daylight savings, which shifted clocks back an hour on November 3 this year and would account for the discrepancy.

‘If someone handed that over and says, “Hey, by the way, this one, we never set it back from daylight savings time,’ you’d need that in an affidavit,”‘ O’Shea said.

Mangione is currently languishing in a Pennsylvania state prison. He is set to appear in a Blair County court for a preliminary hearing on Thursday.

Dickey previously opposed the Manhattan DA’s attempt to extradite his client to New York, but Bragg said last week that he expects this opposition to be dropped after Thursday’s hearing.