CCTV reveals suspect’s key movements just before killing UnitedHealthcare CEO Brian Thompson

CCTV footage may be the key to finding the person who shot and killed the CEO of UnitedHealthcare Brian Thompson.

Thompson, 50, was shot after exiting the Hilton Hotel on Wednesday (December 4) at 6.46am in Manhattan, New York City, where he'd been to attend a investor's conference hosted by the company, which was later cancelled following the shooting.

According to the New York Police Department (NYPD), the gunman appeared to have been 'lying in wait' for the 50-year-old before unloading several bullets into him from behind, arguing that this attack 'does not appear to be a random act of violence'.

Thompson was shot at least once in his back and right calf - while the bullets and casings reportedly had the words 'deny', 'depose' and 'defend' inscribed on them, according to police sources from ABC News and The New York Post.

He was rushed to Mount Sinai Hospital in a critical condition but was later pronounced dead upon arrival.

Brian Thompson was killed in New York (UnitedHealth Group)

None of Thompson's belongings were taken from his person and a motive is yet to be determined by police, although his wife, Paulette Thompson, told NBC News that she was aware that there have been threats made against him.

"I don’t know details. I just know that he said there were some people that had been threatening him." she said.

Cops are now focusing on surveillance footage that details the suspect's key movements just before fatally shooting Thompson.

CCTV footage shows him pictured at a nearby Starbucks with his mask low enough to reveal part of his nose - which investigators are now putting through facial recognition software in a bid to find a match, the BBC reports.

According to the New York Post, the suspect fled on foot down a nearby alleyway before returning to 6th Avenue, where the shooting took place, a little further up the street when he hopped on an electric bike.

The suspect was pictured on CCTV before shooting Thompson (NYPD)

He then cycles north on 6th Avenue towards Central Park before entering it - where he was last seen at 6.48am.

However, according to police, this is where the CCTV footage gets a bit grainy, The New York Post reports.

Establishing a timeline of events, NYPD Chief of Detectives Joe Kenny told CNN that the gunman walked towards Thompson and 'continues to shoot', adding: "It appears the gun malfunctions as he clears the jam and begins to fire again."

Former FBI special agent, Terry Rankhorn, later told Sky News that the malfunction was likely a result of a 'mismatch between between the 9mm silencer used and what was likely subsonic ammunition."