Shell casings with cryptic words were found at the scene of the shooting of UnitedHealthcare CEO Brian Thompson, who was killed outside a Manhattan hotel in New York, law enforcement officials say.

According to NPR member station WNYC’s Gothamist, officials confirmed reports that the words “deny,” “defend” and “depose” were written on the shell casings, but did not say how many shell casings were found. The words are similar to the title of a 2010 book Postpone, Deny, Defend: Why Insurance Companies Won’t Pay Claims and What You Can Do About Itby Jay M. Feinman.

A manhunt for the shooter is underway as police try to piece together details surrounding Thompson’s death early Wednesday morning.

On Thursday morning, the NYPD released a photo of a person involved in the shooting.

Here’s what we know so far.

The suspect “appeared to be waiting for his target”

The suspect lay in wait “for several minutes” outside New York’s Hilton Midtown Hotel before Thompson, who was there for an annual investor conference, arrived, NYPD Police Commissioner Jessica Tisch said said during a press conference on Wednesday.

As Thompson entered the hotel, the suspect approached him from behind and fired several shots, hitting him “at least once in the back and at least once in the right calf,” Tisch said.

During the shooting, the gun jammed several times, but the gunman was able to disengage it and continue firing, NYPD Chief of Detectives Joseph Kenny said, Gothamist reported.

After shooting Thompson, the suspect fled on foot through an alley and then rode away on a bicycle, according to Tisch. The suspect was wearing dark clothing and a mask and “appeared to be waiting for his target,” Tisch also said.

“A highly valued colleague and friend”

Thompson was 50 years old, a husband and father of two children. He joined UnitedHealth Group in 2004 and held several leadership positions before becoming CEO of UnitedHealthcare in 2021.

Before joining UnitedHealth Group, he was a CPA at PricewaterhouseCoopers, an accounting firm, and a manager in the accounting practice’s Transaction Advisory Services group, according to his LinkedIn profile. He received a bachelor’s degree in business administration and accounting from the University of Iowa in 1997.

UnitedHealth Group remembered Thompson as “a valued colleague and friend to all who worked with him.” in a statement on Wednesday.

“We are working closely with the NYPD and ask for your patience and understanding during this difficult time,” the company said. “Our thoughts are with Brian’s family and everyone who was close to him.”

A motive is unclear

The motive for the shooting is still a mystery and police are still searching for the killer. His wife, Paulette Thompson, told NBC News that he was facing threats.

“There had been some threats,” she said. “Basically, I don’t know, a lack of reporting? I don’t know any details. All I know is that he said there were some people who threatened him.”

Surveillance video shows the suspect entering Central Park and a cell phone was found in the alley. All evidence in the preliminary investigation indicates that the shooting of Thompson was a “premeditated, pre-planned targeted attack,” Tisch said.

On Thursday morning, the NYPD released a photo of a person of interest in the shooting.

The NYPD is offering a $10,000 reward to anyone who can provide information about the shooter that could lead to an arrest.

NPR’s Rachel Treisman contributed to this report.