UnitedHealthcare CEO shooting latest: New photos of suspect's face ...

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.

The NYPD has obtained a warrant to search the hostel. Detectives are canvassing other hostels and locations on the Upper West Side and beyond, showing the suspect's picture as they work to identify him, sources told ABC News.

The gunman shot Thompson at close range on Wednesday morning outside a Hilton Hotel where he 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.

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 -- who was caught on surveillance cameras before, during and immediately after the shooting -- had been lying in wait near the hotel.

After Thompson exited his hotel across the street and walked 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 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."

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

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