“They believe he’s not in New York City,” the spokesman added.
An image released on Thursday of the smiling suspect was obtained from a youth hostel the gunman apparently stayed at before the hit, with media reporting he had lowered his mask to flirt with a receptionist.
The FBI, which said it was assisting New York police, offered a reward of up to US$50,000 for information leading to the suspect’s capture.
New evidence emerged on Saturday, a day after authorities located a grey backpack in Central Park thought to belong to the killer. Inside were two items: a jacket and Monopoly money, US media reported.
Police were also looking into the possibility the shooter took the rare step of using a long-barrel veterinary gun – normally used to euthanise animals – to commit the murder.
The gunman on Wednesday walked up behind Thompson of UnitedHealthcare, one of the country’s largest medical insurers, and shot him dead in front of bystanders, an audacious attack captured by a surveillance camera and now seen by millions.
Thompson was attending an investor conference in the Midtown business district.
Police have yet to suggest a motive and would not confirm media reports that the words “delay” and “deny” – language often used by insurance companies to reject claims – were written on shell casings found at the scene.
Video footage shows Thompson on the sidewalk outside the New York Hilton Midtown when a man in a hooded top, his lower face covered, approaches from behind then fires several shots at his 50-year-old victim, who crumples to the ground.
Footage showed the suspect fleeing on foot before getting on a bicycle, with police revealing he headed to Central Park.
Officers have confirmed a cellphone and DNA from a coffee cup were recovered near the murder scene.
In the absence of an arrest, speculation has been rife that the gunman may have sought to take revenge for adverse medical coverage decisions made by the insurer.
UnitedHealthcare is a major player in the lucrative American healthcare market, and the parent group had revenues of US$100.8 billion in the third quarter of the year.
- Agence France-Presse