New York City police are reportedly narrowing down the identity of the suspect in the fatal shooting of UnitedHealthcare CEO Brian Thompson. Investigators believe the shooter arrived in New York City from Atlanta via bus last month, law enforcement sources told ABC News.

The suspect is believed to have traveled through the Port Authority Bus Terminal, and detectives are reviewing surveillance footage to trace his movements, according to sources. A Greyhound spokesperson confirmed the company is cooperating with the NYPD but declined to provide further details.

Police sources revealed that the suspect checked into the HI New York City Hostel on Amsterdam Avenue and 104th Street on November 30. Detectives are working to piece together his activities in the city before that date using additional video evidence.

New photos released by the NYPD on Thursday show the suspect without a mask, reportedly taken during his stay at the hostel. According to a law enforcement source, the unmasked image was captured when the suspect, while flirting with the front desk clerk, removed his mask at her request to show his smile. The surveillance camera recorded his face during the brief moment.

This image is a critical development, with police confident that it could help someone recognize the suspect.

Investigators discovered that the suspect shared a fourth-floor room at the hostel with two other men. He checked in using a New Jersey driver’s license that does not belong to him, police sources said.

Detectives have run the name from the license but found no matches to the suspect’s known appearance or the evidence collected so far.

The search for the suspect continues as investigators work to gather more details about his movements and identity. Authorities are urging anyone who recognizes the individual from the released photos to come forward to assist in solving this high-profile case.