The wife of a top health insurance CEO who was shot dead outside a New York hotel said her husband had spoken about threats against him, possibly related to insurance coverage.

Brian Thompson, 50, CEO of UnitedHealthcare – America’s largest health insurer – was shot in the back by a gunman waiting for him on the sidewalk on Wednesday (US time).

Police said the attack – which was caught in dramatic CCTV footage – appeared to be targeted and premeditated.

New photos of the suspect have been released to try to identify and track down the shooter, who remains on the run.

“Many people passed the suspect, but he appeared to wait for his intended target,” New York Police Department commissioner Jessica Tisch said.

Thompson’s wife Paulette told NBC her husband had received “some threats” in the past.

She was unsure what the threats related to, but she believed they  were linked to health insurance coverage.

“Basically, I don’t know, a lack of [medical] coverage? I don’t know details,” she explained.

“I just know that he said there were some people that had been threatening him.”

Brian Thompson was killed in a ‘targeted’ attack outside a New York hotel. Photo: United Health Group)

The “shattered” wife also released a statement in response to the “senseless killing of our beloved Brian”.

“Brian was an incredibly loving, generous, talented man who truly lived life to the fullest and touched so many lives.

“Most importantly, Brian was an incredibly loving father to our two sons and will be greatly missed.

“We appreciate your well wishes and request complete privacy as our family moves through this difficult time.”

Thompson rose to chief executive after two decades with the firm and earned a pay packet in the millions of dollars.

He was named UnitedHealthcare CEO in April 2021 after working at the company since 2004 in several departments, according to its website.

The BBC reports he made $US10 million ($15.54 million) last year and $9.8 million ($15.23 million) the year before that.

The Wall Street Journal reported in February that Thompson faced allegations of insider trading.

A class-action lawsuit in May alleged Thompson sold $15 million ($21.31 million) of his UnitedHealth shares when he knew the company was under federal investigation.

A reward has been posted for information relating to the suspect. Photo: AAP

Police provided a timeline of the suspect’s movements as he lay in waiting and killed Thompson before fleeing on foot and being seen riding an e-bike through Central Park.

The man, carrying a grey backpack, arrived at the location outside the Hilton hotel on foot about five minutes before Thompson.

He stood along the building line as numerous other people and pedestrians passed by.

At 6.44am, the victim walked towards the Hilton Hotel from across the street, apparently to attend an investors’ conference.

The gunman approached the victim from behind and shot him in the back.

“The shooter then walks toward the victim and continues to shoot,” said NYPD Chief of Detectives Joe Kenny.

“It appears the gun malfunctions as he clears the jam and begins to fire again.”

There was an emergency call, and officers arrived to find Thompson on the footpath with gunshot wounds to his back and leg.

“At the scene, we recover three live nine-millimetre rounds and three discharged nine-millimetre shell casings.”

Thompson was rushed to a nearby hospital, where he was pronounced dead.

“This does not appear to be a random act of violence,” New York City Police Commissioner Jessica Tisch said.

“Every indication is that this was a premeditated, pre-planned, targeted attack.”

The crime scene outside the Hilton Hotel on Sixth Avenue. Photo: AAP

UnitedHealth Group said Thompson was a highly respected colleague and friend to all who worked with him.

“We are working closely with the New York Police Department and ask for your patience and understanding during this difficult time,” it said in a statement.

“Our hearts go out to Brian’s family and all who were close to him.”

UnitedHealthcare is the largest US health insurer, providing benefits to tens of millions of people, who pay more for healthcare than in any other country.

The shooting happened not long before a scheduled investor conference at the Hilton.

UnitedHealth Group Chief Executive Andrew Witty took the stage about one hour after the event started to announce the rest of the program would be cancelled.

“We’re dealing with a very serious medical situation with one of our team members, and as a result, I’m afraid we’re going to have to bring to a close the event today,” he said.

Police tape blocked off the area on 54th Street outside the Hilton on Wednesday morning. Blue plastic gloves were strewn about and plastic cups appeared to mark the location of bullet casings.

“The police were here in seconds. It’s New York. It’s not normal here at seven in the morning but it’s pretty scary,” said Christian Diaz, who said he heard the gunfire from the nearby University Club Hotel where he works.

Police said the shooting would not affect the annual Christmas tree lighting at Rockefeller Centre, a few blocks from the Hilton. The popular event was scheduled for Wednesday night.

-with AAP