UnitedHealthcare chief executive Brian Thompson was shot and killed on Wednesday morning in what police said was a “brazen, targeted attack” outside a Manhattan hotel where the health insurer was holding an investor conference.

The 50-year-old executive was shot at about 6.45am as he walked alone to the New York Hilton Midtown from a nearby hotel, police said.

The gunman appeared to be “lying in wait for several minutes” before approaching Mr Thompson from behind and opening fire, New York City Police Commissioner Jessica Tisch said. Police have not yet established a motive.

“Many people passed the suspect, but he appeared to wait for his intended target,” Ms Tisch said, adding that the shooting “does not appear to be a random act of violence”.

UnitedHealthcare chief executive officer Brian Thompson was shot several times (AP Photo/UnitedHealth Group via AP)

Mr Thompson was struck at least once in the back and once in the calf, Ms Tisch said. He was taken to a hospital, where he was pronounced dead.

The suspect, dressed in a hooded sweatshirt and carrying a grey backpack, then fled on foot down an alleyway before pedalling an e-bike into Central Park a few blocks away.

The shooter was at large, sparking a search that included police drones, helicopters and dogs.

“We are deeply saddened and shocked at the passing of our dear friend and colleague Brian Thompson, the CEO of UnitedHealthcare,” the insurer’s parent company, UnitedHealth Group, said in a statement.

Members of the New York police crime scene unit investigate the scene where Brian Thompson was killed (AP Photo/Stefan Jeremiah)

“Brian was a highly respected colleague and friend to all who worked with him,” the company said. “We are working closely with the New York Police Department and ask for your patience and understanding during this difficult time.”

Police issued a poster showing a surveillance image of the suspect pointing what appeared to be a gun and another image that appeared to show the same person on a bicycle.

Police offered a reward of up to 10,000 US dollars (£7,860) for information leading to an arrest and conviction.

The killing shook a part of New York City that is normally quiet at that hour, happening about four blocks from where tens of thousands of people are set to gather on Wednesday night for the annual Rockefeller Centre Christmas tree lighting.

Mr Thompson’s wife, Paulette Thompson, told NBC News that the executive told her “there were some people that had been threatening him”. She said she did not have details, but suggested they may have involved issues with insurance coverage.

UnitedHealthcare is the insurance arm of the health care giant UnitedHealth Group.