He gunned down a CEO and escaped by bike. Who killed Brian Thompson?

Investigators are searching for clues that could help them identify the masked gunman who stalked and killed the leader of one of the largest U.S. health insurance companies on a Manhattan sidewalk, then disappeared into Central Park.

UnitedHealthcare CEO Brian Thompson died in a dawn ambush on Dec. 4 as he walked to the company’s annual investor conference at a Hilton in Midtown, blocks from tourist draws like Radio City Music Hall and the Museum of Modern Art.

The killing, and the shooter’s movements in the minutes before and afterward, were captured on some of the multitudes of security cameras present in that part of the city.

One video showed him approach Mr. Thompson from behind, level his pistol, and fire several shots, barely pausing to clear a brief gun jam while the dying health executive tumbled to the pavement.

Other security cameras captured the initial stages of the gunman’s escape. He was seen fleeing the block across a pedestrian plaza, then escaping on a bicycle into Central Park, where he vanished.

Police used drones, helicopters, and dogs in an intense search, but the killer’s whereabouts remained unknown late into the night.

New York City Police Commissioner Jessica Tisch said that while investigators had not yet established a motive, the shooting was no random act of violence.

“Many people passed the suspect, but he appeared to wait for his intended target,” Ms. Tisch said at a Dec. 4 news conference.

“From watching the video, it does seem that he’s proficient in the use of firearms as he was able to clear the malfunctions pretty quickly,” NYPD Chief of Detectives Joseph Kenny said.

Police issued several surveillance images of the man, who wore a hooded jacket and a mask that concealed most of his face and wouldn’t have attracted attention on a frigid winter day. Some of the photos were taken at a Starbucks coffee shop shortly before the shooting.

The police department offered a reward of up to $10,000 for information leading to an arrest and conviction.

“Brian was a highly respected colleague and friend to all who worked with him,” the insurer’s Minnetonka, Minnesota-based parent company, UnitedHealth Group Inc., said in a statement. “We are working closely with the New York Police Department and ask for your patience and understanding during this difficult time.”

Mr. Thompson’s wife, Paulette Thompson, told NBC News that he told her “there were some people that had been threatening him.” She didn’t have details but suggested the threats may have involved issues with insurance coverage.

Eric Werner, the police chief in the Minneapolis suburb where Mr. Thompson lived, said his department had not received any reports of threats against the executive.

Investigators recovered several 9 mm shell casings from outside the hotel and a cellphone from the alleyway through which the shooter fled. They were also searching Mr. Thompson’s hotel room, interviewing his UnitedHealthcare colleagues and reviewing his social media, Mr. Kenny said.

Police initially said the shooter rode into Central Park on a bicycle from the city’s bike-share program, CitiBike. But a spokesperson for the program’s operator, Lyft, said police officials informed the company the afternoon of Dec. 4 that the bike was not from the CitiBike fleet.

Health care giant UnitedHealth Group was holding its annual meeting with investors to update Wall Street on the company’s direction and expectations for the coming year. The company ended the conference early in the wake of Mr. Thompson’s death.

Mr. Thompson, a father of two sons, had been with the company since 2004 and served as CEO for more than three years.

UnitedHealthcare is the largest provider of Medicare Advantage plans in the U.S. and manages health insurance coverage for employers and state and federally funded Medicaid programs.

Minnesota Gov. Tim Walz posted on the social platform X that the state is “sending our prayers to Brian’s family and the UnitedHealthcare team.”

“This is horrifying news and a terrible loss for the business and health care community in Minnesota,” the Democrat wrote.

This story was reported by The Associated Press. AP writers Tom Murphy, Steve Karnowski, and Anthony Izaguirre contributed to this report.