Police found the message on bullet casings at the scene where Brian Thompson was killed

Police in New York City are looking into the possible meaning of three words carved into bullets used to target UnitedHealthcare CEO Brian Thompson.

Thompson, 50, was killed in what police described as a ‘brazen, targeted’ attack outside the New York Hilton Midtown hotel at around 6:40am local time on Wednesday (December 4).

Police believe the shooter had been lying in wait at the hotel for Thompson, who was widely known to be in Manhattan for the UnitedHealthcare investors conference, which was scheduled to start at 8am.

After reviewing CCTV footage from the area, NYPD Commissioner Jessica Tisch said: “People passed the suspect, but he appeared to wait for his intended target.”

NYPD Chief of Detectives Joe Kenny added that Thompson’s death ‘does not appear to be a random act of violence‘, though a motive for the attack has yet to be established.

Upon investigating the scene, New York Police Department officers reportedly found shell casings with the words ‘deny’ ,’defend’ and ‘depose’ written on them.

Now, a police source has reported to The New York Post that investigators are looking into the words that bear resemblance to a 2010 book condemning the health insurance industry.

Thompson was the CEO of UnitedHealthcare (UnitedHealth Group)

Written by Rutgers Law School professor Jay M. Feinman, the book is titled: “Delay, Deny, Defend: Why insurance companies don’t pay claims and what you can do about it.”

According to the source, police are considering possible ties to the book as well as more general references to the health industry as a potential motive for the shooting.

Feinman has not commented on whether the message-giver referenced his book.

Following Thompson’s death, his estranged wife, Paulette Thompson, told NBC News that the CEO had been the subject of threats prior to his death.

Police found the casings at the scene (Spencer Platt/Getty Image)

“I don’t know details. I just know that he said there were some people that had been threatening him,” she said.

Paulette described the death of her husband as ‘senseless’, adding: “Brian was an incredibly loving, generous, talented man who truly lived life to the fullest and touched so many lives. Most importantly, Brian was an incredibly loving father to our two sons and will be greatly missed.”

After shooting Thompson, the suspect in the case ran into an alley before fleeing on a bike into Central Park. Police are still on the hunt for the killer and are urging the public to call Crime Stoppers at 1-800-577-TIPS with any information.