Smiling suspect seen in new images as New York police hunt killer of healthcare executive Brian Thompson

New images have been released of the suspect wanted over the targeted murder of a healthcare boss in New York City.

Brian Thompson, the chief executive of UnitedHealthcare, was gunned down outside a Manhattan hotel yesterday morning before the start of a conference.

Police say the gunman was wearing a mask and footage shows him walking slowly behind Mr Thompson before shooting him several times in the back.

Mr Thompson, 50, who headed one of the largest US health insurance companies, was ambushed at 6.45am local time on Wednesday as he walked to the company's annual investor conference at a Hilton in Midtown.

The attacker fired multiple times at Mr Thompson and continued despite the gun briefly jamming, according to police.

He then escaped the scene on an e-bike towards Central Park.

In new pictures released by police, the suspect can be seen smiling in a hostel on the Upper West Side.

Police have searched a room in the building and are investigating whether the suspect paid with cash and used fake identification.

A statement by Mr Thompson's family says they are "shattered" by the "senseless killing".

"Brian was an incredibly loving, generous, talented man who truly lived life to the fullest and touched so many lives," they said in a statement obtained by KARE, a local affiliate of Sky News's US partner network NBC.

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

"We appreciate your condolences and request complete privacy as our family moves through this difficult time."

Hours after Mr Thompson's death, two homes reportedly belonging to his family in Maple Grove, Minnesota, were the targets of a bomb threat.

Police said they believe it was a case of swatting, a felony occurring when one falsely reports an emergency with the intent of dispatching police to an address.

"No devices or suspicious items were located during the investigation," a statement from the police read, local media reports.

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A law enforcement official said the gunman used ammunition emblazoned with the words "deny," "defend" and "depose" in the attack.

The words on the ammunition may have been a reference to strategies insurance companies use to try to avoid paying claims.

New York Mayor Eric Adams, who is a retired NYPD captain, told MSNBC's Morning Joe programme that what had "shocked" them was the fact the shooter used a silencer, something he had never encountered "in all of my years in law enforcement".

A former FBI special agent, Terry Rankhorn, told Kay Burley on Sky News Breakfast the footage of the shooting was "chilling".

"What you can determine from his behaviour is this person is a practised, seasoned, trained professional killer," Mr Rankhorn said.

"He doesn't run up like an inexperienced, emotional but amateur killer... this person calmly walks out," he added.