What is the meaning of the three sinister words police found on the shell casings used by the Manhattan United Healthcare CEO killer?

Three chilling words, “deny,” “defend,” and “depose,” have been found on bullet shell casings recovered at the scene of United Healthcare CEO Brian Thompson‘s apparent targeted assassination Wednesday morning in Manhattan.

The investigation is ongoing, and a suspect remains at large, but the words relate to the insurance industry and could suggest a motive for the crime.

A masked gunman shot and killed Thompson, 50, outside a Manhattan hotel around 6:45 a.m. on Dec. 4. ahead of an investor’s meeting for Thompson’s company, United Healthcare. At a press conference, New York police confirmed the killer waited in ambush for Thompson, targeted in a deliberate attack.

The exec’s wife confirmed her husband had received threats before traveling to New York from Minnesota, where Thompson lived.

“Yes, there had been some threats,” Thompson’s wife, Paulette Thompson, told NBC News. “Basically, I don’t know, a lack of coverage? I don’t know details. I just know that he said there were some people that had been threatening him,” Paulette said.

Despite the risk, Thompson traveled to Manhattan without security and left the hotel alone and on foot.

The words echo a 2010 book critical of the insurance industry

Two of the three words on the shell casings could be taken from Jay M. Feinman’s 2010 book Delay, Deny, and Defend: Why Insurance Companies Don’t Pay Claims.

The book’s website says, “Your insurer’s main objective is not to protect you; in fact, insurers often try to avoid paying justified claims. Today the name of the game is delay, deny, defend: to improve their profits, insurance companies delay payment of justified claims, deny payment altogether, and defend their actions by forcing claimants to enter litigation.”

There has been no official confirmation the assassin read Feinman’s book, and The New York Times reports that Feinman, a Rutgers Law School professor emeritus, declined to comment.

Moreover, the BBC reports that Thompson has been accused of insider trading. Thompson is accused of selling millions of dollars worth of his United Healthcare shares in 2010 amid a U.S. Justice Department antitrust investigation.

Also, just last month, the Justice Department sued to stop a proposed United Healthcare acquisition of home health and hospice provider Amedisys.

In a statement, United Health Group wrote the acquisition would be “pro-competitive and further innovation, leading to improved patient outcomes and greater access to quality care. We will vigorously defend against the DOJ’s overreaching interpretation of the antitrust laws.”

Last fall, Thompson’s company, among other insurance companies, was mentioned in a Senate committee report criticizing the industry for denying what the industry calls “post-acute care” for seniors after falls and strokes.

Suspect remains at large; NYPD releases photos

New York police have released photos of the suspected gunman captured on security camera footage. Sources told ABC News he was spotted on security footage around 5 a.m. at a public housing project on Manhattan’s Upper West Side, carrying what appeared to be an E-bike battery.

The suspect was seen at a Starbucks only moments before the attack and arrived at the scene of the crime about 5 minutes before Thompson exited the building on foot. The suspected gunman used a silencer. He shot Thompson once in the back and continued firing once Thompson fell to the ground.

He then fled into an alley, where a cell phone believed to have belonged to the suspected killer was found, and then fled on a bike, which investigators believe he may have left there in advance.

John Nielsen, 50, a Danish man staying at a hostel in the Upper West Side near where the suspect was seen, said there was a massive police presence near the hostel where Nielsen was staying Wednesday evening. Investigators have said the suspect may have stayed there, too.

Referring to the hostel, Nielsen told The Times, “That the person stays this place, that’s not clever, because there is recording, video all over the place. You don’t check in in a place with so many people.”