Shell casings found at the Midtown crime scene where UnitedHealthcare CEO Brian Thompson was shot Wednesday had cryptic words scrawled on them, NYPD officials confirmed Thursday morning.

The shooting took place outside a Midtown Hilton Hotel, where Thompson was attending an investor conference. Police officers said they executed a search warrant at another nearby hotel where Thompson was staying. Police also said they visited hostels on the Upper East and Upper West Sides as part of their investigation.

Police officials did not say how many shell casings the NYPD had seized, but confirmed reports that they included the terms “deny,” “defend” and “dumping.” The police were unable to provide any further information about the contents.

The words on the bullet casings could shed light on the motive of the shooter, who officials said carried out a targeted, premeditated attack on the 50-year-old manager outside New York’s Hilton Midtown Hotel on Sixth Avenue, where UnitedHealth Group’s annual event was taking place The investor conference was scheduled to take place on Wednesday.

In online forums, several users noted the similarity to the name of Jay M. Feinman’s 2010 book “Delay, Deny, Defend: Why Insurance Companies Don’t Pay Claims and What You Can Do About It.”

Police also released new images Thursday that they said showed a man being questioned in connection with the shooting – the first images of their kind showing the man without a mask. Police did not immediately disclose when and where these images were taken.

As of Thursday morning, police had not arrested or charged any suspects. Police said the gunman was last seen on an e-bike in Central Park on Wednesday morning. She added that she was examining surveillance videos in the area and using dozens of drones to track his movements.

This is a developing story based on preliminary police information and may be updated.