The chief executive of UnitedHealth’s insurance arm was fatally shot outside a hotel in New York City Wednesday morning in a targeted attack, police said.

A manhunt is underway for a suspect who was lying in wait for the executive, Brian Thompson , and fled after shooting Thompson in the back and leg. Police said Thompson lived in Minnesota and was in New York to attend an investor meeting.

Brian Thompson.

He was shot in the chest and leg shortly before UnitedHealth was set to hold its annual investors meeting. The company ended the meeting early.

The New York City Police Department said a 50-year-old man was shot around 6:45 a.m. near a Hilton hotel on Sixth Avenue in Midtown Manhattan. Police officers found him unconscious. He was taken to a hospital in critical condition and later pronounced dead.

Police are still searching for the suspect, who fled north, but said they didn’t believe there was any threat to the public. He was wearing a black face mask and black jacket. Police said they didn’t know the suspect’s motive and are offering a reward of up to $10,000 for information about the shooting. They were set to provide further information at a news briefing later Wednesday morning.

“Our preliminary investigation is revealing that this was not a random act of violence,” Mayor Eric Adams told reporters Wednesday. “It appears as though this was a targeted murder.”

UnitedHealth Group is a healthcare giant that includes the biggest American health insurer as well as doctor groups and other assets. Thompson was the CEO of its insurance unit, UnitedHealthcare.

The company is based in Minnesota, but top executives were in New York on Wednesday for its annual investor day.

The company abruptly cut off its investor event due to the attack. Andrew Witty , chief executive of the parent company, came onstage around 9 a.m. to say that the company was “dealing with a very serious medical situation with one of our team members” and would end its live presentation.

A United Healthcare spokesman said they had not determined if the conference would continue.

A worker who said he witnessed the shooting said the shooter ran past him in gloves and a mask. He said the shooting happened just outside the Hilton parking garage where police cordoned off the area. A spilled box of mints was visible on the ground at the scene.

At around 6 a.m. local time, a man without credentials came to the second floor of the Hilton hotel, where there was a breakfast, according to a hotel worker. “He was in the building,” the person said. He was seen pacing in a corporate park across the street from the 54th Street entrance starting around 6:15 a.m., the worker said.

“Usually there’s a lot of security on the second and third floor,” the worker said. “But not outside.”

Near a side entrance to the hotel, authorities blocked off 54th Street between Sixth and Seventh Avenues with yellow police tape Wednesday morning. Bystanders craned their necks to get a view of the crime scene.

A New York Hilton Midtown spokesperson said the company was saddened by the shooting and directed further questions to police.

Thompson, a longtime UnitedHealth veteran, took over as leader of the insurance unit in 2021. Before that, he oversaw the insurer’s Medicare and Medicaid businesses. He began working at the company in 2004. He graduated from the University of Iowa in 1997 with a business degree, according to his LinkedIn page.

Antonio Ciaccia , who is CEO of 46brooklyn Research, a nonprofit drug-pricing analytics group, said he met Thompson around 2018.

“In working with him, he was uniquely affable, thoughtful, and likable, and I had a genuine respect for him. His death is a shock, and I’m disgusted with the circumstances that led to it,” he said.

As executive vice president of UnitedHealth Group and CEO of UnitedHealthcare, Thompson last year earned $1 million in base salary and $8 million in stock and option awards, according to the company’s  proxy statement . His total pay over the past three years averaged $9.92 million, the document showed.

Minnesota leaders including Gov. Tim Walz , Sen. Amy Klobuchar and Minneapolis Mayor Jacob Frey on social-media said they were horrified by the news and expressed condolences for his family and colleagues.

Write to Alyssa Lukpat at alyssa.lukpat@wsj.com and Anna Wilde Mathews at Anna.Mathews@wsj.com

Corrections & Amplifications undefined Brian Thompson was chief executive of UnitedHealthcare, the insurance arm of UnitedHealth Group. An earlier version of this article incorrectly said Thompson was the CEO of UnitedHealth. (Corrected on Dec. 4)