MIDTOWN (WABC) – Police in New York City appear to be closing in on the identity of the suspect wanted in the fatal shooting of UnitedHealthcare CEO Brian Thompson, believing the shooter arrived in New York on a bus from Atlanta last month , law enforcement sources told ABC News.

According to the sources, the suspected shooter was passing through the Port Authority Bus Terminal and investigators wanted to see if they could recognize him on video.

A Greyhound spokesman said it was cooperating with the NYPD investigation but was “unable to comment further at this time.”

Police sources also told ABC News that the suspect checked into the HI New York City Hostel at 104th Street and Amsterdam on the Upper West Side on November 30. He is believed to have arrived in the city before that date and investigators are continuing their video searches to gain a more complete picture of his movements.

The new developments come after the NYPD on Thursday released new photos of the suspect without a mask, apparently from when he was staying at the hostel. A law enforcement source told Eyewitness News that the suspect’s unmasked smile came about when he flirted with the receptionist who checked him into the hostel and encouraged him to drop the mask so she could see his smile. The suspect obeyed and pulled down his mask long enough for the security camera to capture his face.

It represents an important image for investigators and police are confident someone will recognize him.

The suspect apparently shared a fourth-floor room with two other men and checked into the hostel with a New Jersey driver’s license that did not belong to him, police sources told ABC News.

Investigators ran the name and found it did not match known photos of the suspect or other evidence collected so far, the sources said.

Separately, surveillance footage reviewed by police shows someone who appears to be the suspect exiting the subway before the shooting at the 57th Street station, just blocks from the crime scene. On surveillance footage, the suspect was seen outside the hostel around 5 a.m. on Wednesday, apparently holding an e-bike battery.

The police are currently investigating whether the suspect prepositioned the bicycle and rode the subway to the crime scene.

The ammunition loads and shell casings discovered at the scene of Wednesday morning’s shooting bore the words “deny,” “defend” and “cancel,” which investigators interpret as a possible message from the suspect.

It supports their work motive that the suspect had a grudge against the insurance company. They will investigate any dispute or denial of service that is brought against the company and will respond to any threat made against UnitedHealthcare’s CEO.

Thompson, 50, of Minnesota, was shot about 6:45 a.m. outside the New York Hilton on Sixth Avenue between 53rd and 54th streets in what police said was a “brazen targeted attack.”

The CEO was in New York City for an investor conference at the Hilton, and his schedule was well known.

NYPD officers tracking the sale of the type of gun used to kill the UnitedHealthcare CEO arrived Thursday at a store in Connecticut that was selling the same type of gun, according to police sources.

Police believe the shooter used a B&T Station Six, known in Britain as the Welrod pistol.

The weapon does not have a silencer, but rather a long barrel that allows the 9mm cannon to fire an almost silent shot.

This requires the ammunition to be manually removed from the magazine, which is consistent with what is seen in the video of the shooting. The weapon is not easy to obtain, so investigators checked all recent purchases.

The actual weapon used in the shooting of Thompson has not been recovered, so this is an investigative lead that authorities are following.

The gunman appeared to know which door Thompson would enter and was seen on video loitering around the hotel at least five minutes before the shooting. Thompson was attacked from behind and fired several shots at the West 54th Street door at close range, including several shots in the back and once in the right calf.

At some point the gun appeared to jam. After clearing the traffic jam, the suspect resumed shooting.

It’s not clear if any words were exchanged before the shooting.

The shooter is described as 6 feet tall, tall and slim, wearing a black jacket, black hat, black ski mask and black backpack. He ran down Ziegfeld Alleyway in the middle of the block, eventually hopped on a bike and rode off into Central Park.

A new video released Thursday shows the alleged suspect leaving Central Park on West 85th Street on a bicycle after the shooting.

Investigators also recovered surveillance images from a Starbucks a block north where the suspect was several minutes before the shooting, and a cellphone was found along the escape route.

Although a suspect has not yet been identified, police expect to find good forensic evidence from a water bottle and two Power Bar wrappers that were discarded at the same Starbucks where police also obtained the suspect’s surveillance video. They say the unspent shell casings and the cellphone, which now has a search warrant, will also help in their investigation.

There is a $10,000 reward for information.

ABC News contributed to this report.

READ MORE: What we know about the shooter in the killing of UnitedHealthcare CEO Brian Thompson

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