Authorities Examining DNA Evidence of Suspect in UnitedHealthcare CEO Brian Thompson's Murder

The suspect stayed at an Upper West Side hostel prior to the shooting

New York City police have recovered DNA evidence from the suspect in the fatal shooting of UnitedHealthcare CEO Brian Thompson.

The sample has been taken to the New York City Chief Medical Examiner's office for analysis, a spokesperson for the Medical Examiner confirms to PEOPLE. It wasn't immediately clear what kind of sample was taken nor where it was taken from.

The New York Post reported, however, that the DNA was recovered from a water bottle left at the scene — from which police also swept fingerprints — as well as the bullet casings at the scene of the murder. The casings were engraved with the words "deny," "defend," and "depose," similar to a phrase — "delay, deny, defend" — used to describe a strategy of insurance companies rejecting claims.

Related: Suspect in CEO Brian Thompson Shooting Smiled Because He Was Flirting with Hostel Staffer: Reports

Thompson was fatally shot in front of the New York Hilton Midtown hotel early in the morning on Wednesday, Dec. 4, in what police have said was a deliberate, targeted killing. A motive has not yet been established.

Police believe that, based on surveillance video of the shooting, the suspect is "proficient" in the use of firearms.

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Related: UnitedHealthcare CEO Was Separated from Wife at Time of Midtown Manhattan Fatal Shooting: Report

Police on Thursday released images of a smiling suspect taken from a hostel he is believed to have stayed at on the Upper West Side. Unlike earlier surveillance images taken from just prior to the shooting, the suspect's face was unmasked. Reportedly, the suspect pulled down his face mask to flirt with a hostel employee, per CNN and ABC, which cite police sources.