The NYPD has clear footage of the killer who opened fire on the CEO of UnitedHealthcare Brian Thompson in Midtown Manhattan… but only behind the suspect.

Police released surveillance images taken Wednesday morning outside the Hilton Hotel at 6th Avenue and 54th Street … and they show Thompson, 50, entering the hotel alone around 6:45 a.m. The shooter walks behind him, pulls out a pistol and starts firing from less than three meters away.

It appears the suspect fired his weapon, which was equipped with a silencer, at least three times before fleeing into an alley across the street. Police said he fled on a bicycle, which was caught on another surveillance camera, and rode into Central Park…just a few blocks away.

Witnesses said the cold-blooded killer was masked and waited outside the hotel for at least several minutes before Thompson arrived. The footage appears to support the NYPD’s theory that it was a targeted attack.

The challenge for police is that none of the surveillance images they have released clearly show the suspect’s face – he was wearing a hoodie and carrying a gray backpack – and there is no sound in the footage.

Police said they recovered three 9-millimeter cartridges and shell casings from the scene. They’re offering a $10,000 reward for any information leading to the arrest and conviction of the suspect – while also working with UnitedHealthcare to determine a possible motive… including any recent threats or disgruntled former employees of the health insurance giant.