NEW YORK – Investigators are looking for clues that could help them identify the masked shooter who hunted down and killed the head of one of America’s largest health insurance companies on a Manhattan sidewalk, then disappeared into Central Park.

CEO of UnitedHealthcare Brian Thompson50, died Wednesday in a dawn ambush while walking to the company’s annual investor conference at a Midtown Hilton, just blocks from tourist attractions like Radio City Music Hall and the Museum of Modern Art.

The killing and the shooter’s movements in the minutes before and after were captured on video by some of the multitudes of security cameras in that part of the city.

Video showed him approach Thompson from behind, point his pistol and fire several shots, barely stopping to clear a brief traffic jam as the dying health official fell to the sidewalk.

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

Police used drones, helicopters and dogs to conduct an intense search, but the killer’s fate remained unknown until late at night.

New York City Police Commissioner Jessica Tisch said that while investigators had not yet established a motive, the shooting was not a random act of violence.

“Many people passed the suspect, but he appeared to be waiting for his target,” Tisch said at a news conference Wednesday.

“Looking at the video, it appears that he is very proficient in handling firearms because he was able to eliminate the malfunctions quite quickly,” said NYPD Chief of Detectives Joseph Kenny.

Police released several surveillance images of the man, who wore a hooded jacket and a mask that hid most of his face and would not have attracted attention on a frigid winter day. Some photos were taken at a Starbucks shortly before filming.

The police department has 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,” UnitedHealth Group Inc., the Minnetonka, Minn.-based parent company of the insurer, said in a statement. “We are working closely with the NYPD and ask for your patience and understanding during this difficult time.”

Thompson’s wife, Paulette Thompson, told NBC News that he told her “that some people were threatening him.” She did not have details, but suggested the threats could be linked to insurance coverage issues.

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

Investigators recovered several 9mm shell casings outside the hotel as well as a cell phone in the alley through which the shooter fled. They also searched Thompson’s hotel room, interviewed his colleagues at UnitedHealthcare and examined his social media, Kenny said.

Police initially said the shooter entered Central Park on a bicycle using the city’s bike-sharing program, CitiBike. But a spokesperson for the program’s operator, Lyft, said law enforcement officials informed the company Wednesday afternoon that the bike was not part of the CitiBike fleet.

Healthcare giant UnitedHealth Group was holding its annual investor meeting to update Wall Street on the company’s direction and expectations for the coming year. The company ended the conference shortly after Thompson’s death.

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

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

Minnesota Governor Tim Walz published on the social platform that the state “sends our prayers to Brian’s family and the UnitedHealthcare team.”

“This is horrible news and a terrible loss for Minnesota’s business and health care communities,” the Democrat wrote.

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Associated Press writers Tom Murphy in Indianapolis, Steve Karnowski in St. Paul, Minnesota, and Anthony Izaguirre in Albany, New York, contributed to this story.