Thompson, 50, was set to speak at an investor meeting when he was gunned down about 6.45am (8.45pm AEDT) on Wednesday outside the New York Hilton Midtown by a shooter who fled on foot and then took an e-bike into Central Park, according to the New York Police Department.
Thompson was taken to a hospital but could not be saved. Police were still searching for the shooter as of late morning and no arrests had been made.
Though officials said the attack appeared to be targeted, they did not yet have a motive for the shooting.
Mayor Eric Adams said police were reviewing evidence from the scene, including video.
“It seems to be clearly targeted by an individual and we will apprehend that individual,” Adams said.
UnitedHealthcare is the insurance arm of the health care giant UnitedHealth Group.
The Minnesota-based company was scheduled to have its annual meeting with investors in New York City to update Wall Street on the company’s direction and expectations for the coming year, according to a company media advisory. An announcement was made to attendees Wednesday morning that the conference was ending early.
The Hilton is in a bustling part of Manhattan, a short walk from tourist sites such as the Museum of Modern Art and Rockefeller Centre, and often dense with tourists and office workers on weekday mornings.
The popular Rockefeller Centre Christmas Tree lighting is set to take place on Wednesday evening (Thursday morning AEDT).
Part of the block where the shooting took place was cordoned off with police tape, with a large contingent of police officers at the scene. Many security cameras are nearby.
Thompson had served as CEO for more than three years and had been with the company since 2004.
“This is horrifying news and a terrible loss for the business and health care community in Minnesota,” the Democrat wrote.
UnitedHealthcare is the largest provider of Medicare Advantage plans in the US and manages health insurance coverage for employers and state-and federally funded Medicaid programs.