Police sources say the suspect who shot UnitedHealthcare CEO Brian Thompson outside a Midtown hotel may have left a message on the bullets he used to kill the executive Wednesday morning.

The NYPD is investigating the possible message – which appears to contain the words “deny”, “depose” and “defend” – written on live bullets and shell casings left behind by the masked assassin after he shot the 50-year-old Thompson several times at a distance of about 6:46 a.m. before the escape, the sources said.

Police officers had recovered three live 9-millimeter cartridges and three fired shell casings outside the Hilton Hotel on Sixth Avenue, where Thompson, of Minnesota, was scheduled to host an investor conference, police officials said.

Sources said several of the pieces of evidence contained one word each, suggesting the shooter may have been trying to leave a message.

The masked gunman used a silencer and appeared to be an experienced shooter, according to surveillance footage obtained by the Post.

But he may have made some serious mistakes that could help investigators easily identify him.