After UnitedHealthcare CEO Brian Thompson is shot dead, all the unanswered questions: Who is the mystery witness? Whats on the abandoned phone? And why WAS the assassin in Starbucks?

It has all the hallmarks of a dramatic new spy movie.

At 6.44am on Wednesday, a masked assassin shot dead a multi-millionaire executive on one of New Yorks busiest shopping streets.

After confirming hed eliminated his target, the hooded man walked calmly away, before apparently disappearing into thin air in one the worlds most surveilled cities.

His victim: UnitedHealthcare CEO Brian Thompson, 50, who earned $10 million a year and suffered at least two gunshot wounds – one to the back, the other in his leg – outside the Hilton Hotel on Manhattans Sixth Avenue. He was later pronounced dead in hospital.

It appears to have been a targeted attack, police say, with the assassin lying in wait outside the Hilton for at least five minutes before Thompson emerged from his hotel over the road.

The executive had arrived in the city on Monday and was making his way to his companys annual investor conference, due to be held in the Hilton and at which he was expected to announce bumper predicted revenues of $450 billion. UnitedHealthcare is the largest health insurance provider in the US.

Chilling CCTV footage shows the assassin stepping out from behind a vehicle and shooting Thompson – who didnt see his killer coming – with a large gun that appears to have been fitted with a silencer. The bullet sends Thompson, a married father-of-two, stumbling to the floor while a mystery bystander flees.

The killers gun then appears to jam, prompting him to adjust the weapon, before stepping closer to Thompson and taking another shot.

At 6.44am on Wednesday, a masked assassin shot dead a multi-millionaire executive on one of New Yorks busiest shopping streets.

His victim: UnitedHealthcares CEO Brian Thompson suffered at least two gunshot woundsoutside the Hilton Hotel on Manhattans Sixth Avenue.

Footage surfaced on Wednesday evening showing the assassin loitering in a Starbucks nearby to the Hilton Hotel, minutes before the attack.

Police were called at 6.46am but the killer, carrying a distinctive grey backpack, had already fled the scene on foot.

Making his way through an alleyway, he got onto an electric Citibike, cycling up Sixth Avenue and into Central Park. Hed vanished by 6.48am. There has been no sign of him since.

Despite a frantic manhunt, the offer of a $10,000 reward for information, and all of New York Citys policing might, worryingly little is known about who Thompsons killer is, why he shot him, and where he is now?

Here, the Daily Mail details the the key questions that remain unanswered:

Who is the shooter?

Images from surveillance footage show the shooter to be a light-skinned man wearing a dark jacket, a black face mask, black and white sneaker, and carrying a large grey backpack.

Police do not yet know, or at least have not released, his identity. They say it seems unlikely that he and Thompson had crossed paths before.

The attack does, however, seem to have been premeditated.

He appeared to wait for his intended target, NYPD commissioner Jessica Tisch said Wednesday. I want to be clear: At this time, every indication is that this was a premeditated, preplanned, targeted attack.

Of particular concern is how confidently the gunman appeared to handle his weapon. Indeed, he quickly overcome an apparent jam in the midst of the shooting. There has been speculation he could be a trained killer or is at least experienced with firearms.

The type of gun he used is also important, it is a handgun with what appeared to be a silencer attached. It is illegal to buy or use a silencer in the state of New York.

Who is the mystery bystander?

Footage of the attack shows a figure, who appears to be a woman dressed in dark clothing and holding a coffee cup, fleeing from a doorway as the assassin opens fire just meters away from them.

We do not yet know who the person is, but there has been no suggestion that they were involved or knew Thompson.

Indeed, they appeared to be surprised by the shooting, cowering into the doorway when the shot rang out, before making a run for it.

Police will no doubt be desperate to identify this key witness.

Footage of the attack shows a figure, who appears to be a woman dressed in dark clothing and holding a coffee cup, fleeing from a doorway as the assassin opens fire just meters away from them.

What is on the discarded phone – and where is the shooters bike?

Police recovered a phone from the alley down which the shooter fled. They have not revealed what, if anything, was on the phone, or confirmed that it belonged to the shooter – but they do say they are performing forensic analysis on it.

The shooter fled on foot to Sixth Avenue where he picked up an electric CitiBike and rode up to Central Park, entering on Centre Drive before disappearing.

Police are working with Lyft, the taxi company that owns CitiBike, to track the bike – which is fitted with GPS.

It is not yet clear how the bike was obtained. CitiBikes have to be paid for and users must have memberships - which would mean electronically stored details. The bike could, of course, have been stolen or someone elses membership details could have been used.

What was in the backpack?

Despite a massive ongoing manhunt with drones, dog units, helicopters and officers on the ground, police seem to be no closer to finding the shooter.

His last known location was entering Central Park at 6.48am.

Given the large backpack he was carrying, he may well have had a change of clothes that allowed him to slip out of the park unnoticed.

The atmosphere in the park on Wednesday afternoon was described by reporters on the ground as normal despite the grim news, with runners and walkers going about their usual business.

Police have had more luck tracking the assassins movements before the shooting, with footage surfacing Wednesday evening of him loitering in a Starbucks nearby to the Hilton Hotel and minutes before the attack.

It is not clear whether he ordered anything to eat or drink, or for how long he stayed. In the images he appears to be holding a small object in his hands.

Police are clearly confident that the shooter will be caught or has fled the immediate area, as the annual Christmas tree lighting at the iconic Rockefeller Center – just blocks away – was allowed to go ahead on Wednesday evening. Thousands of New Yorkers and tourists attend each year.

His last known location was entering Central Park at 6.48am. Given the large backpack he was carrying, he may well have had a change of clothes that allowed him to slip out of the park unnoticed. (Pictured: Assassin fleeing the scene on a bike. His backpack is clearly visible).

Thompson is survived by his wife Paulette, 51, and their two sons, who live in the familys $1.5 million home in Maple Grove, Minnesota.

What was the motive?

An official motive for the shooting has not yet been released, but there is widespread speculation online that the shooting was linked to Thompsons job – as the head of a controversial health insurance company.

Thompsons 51-year-old wife, Paulette – with whom he lived in a $1.5 million home in Minnesota – told NBC that her husband had been receiving threats in the days before the shooting.

There had been some threats… Basically, I dont know, a lack of [insurance] coverage? she said, I dont know details. I just know that he said there were some people that had been threatening him.

I cant really give a thoughtful response right now, she added, I just found this out and Im trying to console my children.

The couple shared two sons.

Despite being such a high-profile job, Thompson seems to have kept a low profile and was known by few outside the industry.

He was named as CEO in 2021, leading Uniteds division that deals with Medicare and Medicaid, overseeing the health coverage of more than 49 million Americans, and bringing in $281 billion in revenue for the company in 2023.

The Department of Justice launched an investigation into the company last year, probing whether the insurer was unfairly restricting competitors and running a monopoly.

In May this year, Thompson and other executives were subsequently sued for alleged fraud and insider trading. A complaint lodged by a pension fund claimed Thompson had failed to tell investors about the DoJ probe before unloading 31 percent of his personal company shares, taking $15.1 million in profit.

The complaint alleges that Thompson and other execs sold over $100 million in company stock during the four-month period when insiders knew about the federal investigation, but the public did not.

In February this year, United was hit by one of the largest healthcare data breaches in US history, with the company estimating that as many as one-third of Americans private data — potentially including Social Security numbers — had been compromised.