New York police have "reason to believe" the man they are hunting following the murder of UnitedHealthcare CEO Brian Thompson has left New York City.
Police commissioner Jessica Tisch told CNN that the suspect may have left the state.
Investigators are continuing to search for the man following the brazen attack outside a Manhattan hotel.
Mr Thompson, the CEO of UnitedHealth's insurance unit, was shot from behind on Wednesday morning in what police described as a targeted attack by a masked assailant lying in wait.
It came just before the company's annual investor conference at the Hilton on Sixth Avenue.
The words "deny," "defend" and "depose" were carved into the shell casings found at the scene, police sources told ABC and the New York Post. Reuters has not independently verified that information.
The words evoke the title of a book critical of the insurance industry published in 2010 titled "Delay Deny Defend: Why Insurance Companies Don't Pay Claims and What You Can Do About It."
The author, Jay Feinman, a professor emeritus at Rutgers University Law School, wrote, "Sorry, no comment" in an email when contacted by Reuters.
Authorities have released a new photo with a clear view of the suspect's face, a day after publishing photos that showed his face partially obscured by a ski mask, and have asked the public's help in identifying and locating him.
Police have also searched a hostel on Manhattan's Upper West Side where the suspect is believed to have been staying, CNN reported.
Investigators were still looking for a motive, police officials said at a Wednesday press conference.
"Every indication is that this was a premeditated, preplanned, targeted attack," New York City Police Commissioner Jessica Tisch told reporters on Wednesday.
"Security video showed the shooter behind Thompson, 50, raising his handgun and firing at his back.
"Police said the gunman arrived outside the hotel several minutes before Thompson and waited for him to walk past before firing, ignoring other passers-by.
"The suspect, wearing a hooded sweatshirt and the ski mask and wearing a gray backpack, fled on foot before mounting an electric bike and riding into Central Park," police said.
Police published a number of images of the suspect taken from video cameras in the area, including one with the gun raised and pointed toward Thompson and another of the suspect fleeing on the bike.
The city has a vast network of cameras, largely built following the 11 September 2001 attacks that police can use to track suspects' movements.
The killing took place on the morning of the city's annual Christmas tree lighting at Rockefeller Center a few blocks away.
The event went ahead as planned under heavy security.
UnitedHealth is the largest U.S. health insurer, providing benefits to tens of millions of Americans, who pay more for healthcare than people in any other country.
Thompson, a father of two, had been the CEO of UnitedHealthcare, a unit of UnitedHealth Group, since April 2021.
The company has been grappling with the fallout from a massive data hack of its Change Healthcare unit that provides technology for U.S. healthcare providers, disrupting medical care for patients and reimbursement to doctors for months.
Thompson had worked at UnitedHealth since 2004 in several divisions, according to a biography later removed from the company's website.
"Our hearts go out to Brian's family and all who were close to him," the company said in a statement.
In a video sent to employees, UnitedHealth Group CEO Andrew Witty announced Thompson's death, calling him a "truly extraordinary person."
At its headquarters in Minnetonka, Minnesota, the company lowered flags on campus to half-staff, a spokesperson told Reuters.
Thompson's wife, Paulette, told NBC News on Wednesday that he had been receiving some threats related to his job but said she did not know the details.
"Brian was an incredibly loving, generous, talented man who truly lived life to the fullest and touched so many lives," she said later in a statement.
"Brian was an incredibly loving father to our two sons and will be greatly missed."
In Maple Grove, Minnesota, where Thompson lived, police administrator Theresa Keehn told Reuters there were no reports of threats to Thompson, but there was one reported incident of "suspicious activity" at his home in June 2018.
Ms Thompson was getting ready for bed when she reported seeing the deadbolt turning on their front door, the police report said.
She hid in the bathroom "terrified", but police found no sign of an attempted break-in and no one on the property.
