UnitedHealthcare CEO shooting suspect allegedly flashed smile while flirting with hostel worker

Police appear to be closing in on the identity of the man suspected of gunning down UnitedHealthcare CEO Brian Thompson in Midtown Manhattan, sources told ABC News.

Authorities on Thursday released images of the suspect taken from a surveillance camera at the HI New York City Hostel at West 103rd Street on the Upper West Side, where it appears the suspect shared a room with two other men, according to police sources.

Police were able to find an image of the suspect without his face mask because he was flirting with the woman who checked him into the hostel, police sources told ABC News.

As he stood at the check-in desk, the sources said the woman asked to see his smile. The suspected shooter obliged, pulling down his mask long enough for the surveillance camera to capture his face.

Detectives canvassed other hostels in the area and showed people the suspect's picture, sources said. Police have determined the suspect checked into an Upper West Side hostel using a New Jersey license that isn’t his, police sources told ABC News.

Rather than New Jersey, the individual has been linked most recently to Atlanta, Georgia. The shooter arrived in New York last month on a Greyhound bus from Atlanta, law enforcement sources told ABC News on Thursday.

He arrived through Port Authority Bus Terminal, and detectives have been looking to see if they can spot him on video. Greyhound is cooperating fully with the NYPD investigation, a spokesperson said.

However, the assailant didn't check into the Upper West Side hostel until Nov. 30.

Because it’s believed he arrived in the city prior to that date, detectives are continuing their video canvass to gain a fuller picture of his movements in the weeks preceding the shooting.

The gunman shot Thompson at close range on Wednesday morning outside a Hilton Hotel where the CEO was attending a conference.

The "brazen, targeted attack" was "premeditated," NYPD Commissioner Jessica Tisch said.

Bullet casings found at the scene had the words "deny," "defend" and "depose" written on them, police sources said.

The motive remains unknown, police said.

The gun used in the shooting hasn't been recovered, sources said.

Police believe the shooter used a B&T Station Six, known in Great Britain as a Welrod pistol, according to police sources. The gun doesn't have a silencer but does have a long barrel that enables the 9 mm to fire a nearly silent shot. The gun requires manually cycling ammunition from the magazine.

The weapon is not easily attainable so investigators have been running down all recent purchases, according to police sources. NYPD detectives arrived Thursday at a gun shop in Connecticut that sold a weapon of the same type, sources said.

Thompson, 50, was in New York City for the UnitedHealthcare investors conference, which was scheduled to start at 8 a.m. His schedule was widely known, police sources said.

The suspect appeared to lie in wait near the Hilton Hotel. After Thompson exited his hotel and walked across the street to the Hilton, the masked gunman shot him at about 6:40 a.m., police said.

"The shooter then walks toward the victim and continues to shoot," NYPD Chief of Detectives Joseph Kenny said. "It appears that the gun malfunctions, as he clears the jam and begins to fire again."

The shooter fled on foot into an alley, where a phone believed to be linked to the suspect was later recovered, police sources said.

The suspect then fled on a bike and rode into Central Park, police said.

The shooter was also caught on surveillance video at 5 a.m. Wednesday outside the Frederick Douglass Houses, a public housing project on the Upper West Side, sources told ABC News. That footage showed the suspect carrying what appeared to be an e-bike battery.

Police have recovered a water bottle and candy wrapper from the crime scene which they believe are linked to the gunman. Fingerprint and DNA tests on the items are ongoing, law enforcement sources told ABC News.

Thompson's wife, Paulette Thompson, said in a statement that she is "shattered" by the "senseless killing."

"Brian was an incredibly loving, generous, talented man who truly lived life to the fullest and touched so many lives," she said. "Most importantly, Brian was an incredibly loving father to our two sons and will be greatly missed."

The Thompsons each owned separate homes in the same suburb of Minneapolis and had been living separately for years, according to property records and interviews with neighbors.

A neighbor who asked not to be named called Brian Thompson "a really impressive person" and described Paulette Thompson as "always friendly and very kind."

The neighbor said her husband, who worked with Brian Thompson up to three years ago, thought of him as "the smartest person in the room."

Police urge the public to call Crime Stoppers at 1-800-577-TIPS with any information.

ABC News' Mark Crudele, Mark Guarino and Josh Margolin contributed to this report.