New clues emerge in hunt for gunman who killed health insurance boss

New clues have emerged as investigators hunt for the gunman who shot dead a US health insurance boss in the middle of New York City.

UnitedHealthcare chief Brian Thompson was shot dead outside a Manhattan hotel on Wednesday morning before the start of his company's annual investor conference.

Footage showed the attacker walking up slowly behind Mr Thompson and opening fire outside the Hilton hotel.

New clues

Amid the ongoing investigation, officers are now looking into leads about the suspect's travel before the attack and a message written on the ammunition found at the scene.

It is now believed that the suspect may have travelled to New York late last month on a bus from Atlanta, Sky News' US partner NBC News reported, citing three senior law enforcement officials.

Investigators are working to see if they can find a name from a ticket purchased for a trip on 24 November that could help identify the suspect.

Smiling suspect

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

Police are investigating whether he used a fake ID to stay at the hostel and if he paid in cash.

His room there has been searched.

CNN reported that the picture of the suspect smiling was only obtained after he was asked to lower his mask while flirting with a female employee at the hostel.

The suspect was also pictured at Starbucks before the shooting, and while there purchased a bottle of water and protein bars - which were later found in a rubbish bin and taken to be examined for DNA.

What we know about health boss shooting

New York police commissioner Jessica Tisch said the killer appeared to have been "lying in wait for several minutes" for Mr Thompson to approach the hotel beforehand.

The masked attacker shot Mr Thompson, 50, multiple times at 6.45am local time, and continued despite his gun briefly jamming, according to police.

He then escaped on an e-bike towards Central Park and despite the best efforts of police remains unidentified and at large.

'Deny', 'defend' and 'depose'

The words "deny", "defend" and "depose" were found written on the ammunition used in the attack, referencing a phrase used by health insurance industry critics.

They, according to lawyers and critics, describe tactics used by the health insurance industry to avoid paying claims.

It refers to insurers delaying payment, denying a claim and defending their actions - with UnitedHealthcare a frequent target of criticism from doctors and patients alike.

The reason for the killing remains unknown but New York City police said evidence firmly pointed toward it being targeted.

'Senseless killing'

A statement by Mr Thompson's family said they were "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 NBC.