New evidence suggests the suspect who killed UnitedHealthcare CEO Brian Thompson on Wednesday may have left a message on bullet casings at the crime scene.

Police sources told the New York Post that the words “deny,” “depose” and “defend” were written on the live cartridges and shell casings left behind by the bomber after the shooting.

The evidence also suggested that each bullet and shell casing had only one word on it, leading them to believe he may have been trying to leave a message, sources said.

In a shocking video obtained by Fox News Digital, Thompson is seen walking down a New York City sidewalk when a masked man wearing a black hooded jacket and carrying a backpack appears behind him and raises a handgun.

Security measures have been tightened for the annual Rockefeller Christmas tree lighting after a gunman killed the CEO of UnitedHealtCare

Scene near the Hilton Hotel in Midtown Manhattan, New York, where police say a man was shot Wednesday morning. The victim is reportedly 50-year-old Brian Thompson, CEO of United Healthcare. (Julia Bonavita/Fox News Digital)

The perpetrator fires several shots. At some point the gun appeared to jam. The attacker then appears to slam the weapon on his side as he walks toward the victim, who tries to escape.

After the shooting, the suspect walked between two vehicles, got on a bicycle and then disappeared into Central Park, the New York City Police Department (NYPD) said.

It was previously reported that the suspect was using a Citibike – which can be tracked – but the NYPD has clarified that the incident did not involve such a bike.

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A surveillance image released by the NYPD shows the suspect in the shooting of United Healthcare CEO Brian Thompson on Wednesday, December 4, 2024. (NYPD Crimestoppers)

Investigators hope accompanying evidence left behind will help identify him, including a cellphone found in an alley near the hotel where the shooting occurred and a cup in a trash can at a nearby Starbucks.

UnitedHealth Group released a statement expressing its condolences and surprise at the day’s events.

This 2017 file photo of Brian Thompson was published via Businesswire when he was named chief executive officer of the UnitedHealthcare unit in 2017. (Businesswire)

“We are deeply saddened and shocked by the passing of our dear friend and colleague Brian Thompson, CEO of UnitedHealthcare. Brian was a valued colleague and friend to all who worked with him. We are working closely with the New York Police Department. Please be patient and understanding during this difficult time. Our condolences go out to Brian’s family and everyone who was close to him.

Anyone with information is asked to contact Crime Stoppers at 1-800-577-TIPS or in Spanish, 1-888-57-PISTA. Tips can also be submitted on the Crime Stoppers website at crimestoppers.nypdonline.com.

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Fox News Digital’s Greg Wehner contributed to this report.