Gunman who killed UnitedHealthcare boss Brian Thompson a 'practised, seasoned, trained professional', says FBI expert

Terry Rankhorn told Kay Burley on Sky News Breakfast the footage of the shooting in New York City, which police are treating as a targeted hit, was "chilling".

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

Shell casings, recovered from the scene, had the words "defend", "deny", and "depose" written on them according to Sky News' US partner, NBC News, which spoke to a senior New York City law enforcement official.

"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.

"He paces his target. He draws his weapon. He takes careful aim and then fires at his target once. And then you can see the weapon malfunction.

"He calmly clears the malfunction, fires again, and advances on his target. This isn't some drug-addled murderer. This is a professional."

Security cameras also captured the gunman's escape on an e-bike into Central Park. Police used drones, helicopters and dogs in an intense search, but he has not been traced.

New York City Police Department (NYPD) commissioner Jessica Tisch said the shooting was no random act of violence, but a "premeditated, pre-planned, targeted attack", although the motive is unclear.

"It does seem that he's proficient in the use of firearms as he was able to clear the malfunctions pretty quickly," added Joseph Kenny, NYPD chief of detectives.

Police released images of the man, who wore a hooded jacket and a mask that concealed most of his face.

Mr Rankhorn shared his thoughts about the man's getaway: "He clearly had a preplanned escape route. This is someone who knows their craft. They're practised at it. And, it was an extremely effective and efficient assassination."

"The e-bike is actually a shockingly effective tool in New York City because of the traffic... they can weave in and out of traffic even if he was being pursued by a police-marked vehicle."

How quick it is to remove the traces of a murder, a brazen assassination at that.

Not 12 hours since UnitedHealthcare chief executive Brian Thompson was gunned down in midtown Manhattan and pressure washers were hosing down what was left of the crime scene outside the Hilton hotel.

For now we have no idea whether the gunman was a hired assassin or a man with a personal vendetta.

We have no idea of his motive or of the motive of those who may have paid him.

He had the look of a professional, or one certainly familiar with a gun, but there are millions of Americans who are familiar with guns.

All we do know is he is still on the run after an extraordinary killing, vanished into the many millions who call NYC their home.

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The murdered CEO had been receiving recent threats but hadn't been altering his travel routine, according to his wife Paulette Thompson.

Mr Rankhorn cast doubt on whether that was a major line of inquiry for investigators. "The recipe for murder is: motivation, means and opportunity. It's quite likely that a lot of these threats were just incidental," he said.

"I really, really, really doubt that this is some dissatisfied insurance customer from middle America who flew to New York City and planned out a very professional, well-executed assassination. That just doesn't make sense."

NYPD has offered a reward of up to $10,000 (£7,851) for information leading to an arrest and conviction.

-SKY NEWS