• Police investigating the fatal shooting of UnitedHealthcare CEO Brian Thompson are working on the belief the suspect traveled to New York City on a Greyhound bus from Atlanta two weeks ago.
• The NYPD released photos of a person of interest wanted for questioning Thompson's slaying.
• Thompson was killed by a masked gunman as he headed to the Hilton Hotel for an investor meeting of UnitedHealth Group, UnitedHealthcare's parent company.
• The words "deny," "defend" and "depose" were found on shell casings from the shooting scene.

Police investigating Wednesday's fatal shooting of UnitedHealthcare CEO Brian Thompson now believe the man wanted in connection with the killing traveled to New York City on a Greyhound bus from Atlanta two weeks ago, NBC News reported Thursday night.

Investigators are trying to find a name for the unidentified suspect from ticket purchases for the trip, which ended in New York at around 9 p.m. ET on Nov. 24.

That arrival date was two days before UnitedHealth Group, the parent of UnitedHealthcare, announced that it would hold its annual investor conference in New York on Dec. 4 — the same day that a masked gunman killed the 50-year-old CEO Thompson as he was about to walk into that event in the Hilton Hotel in midtown Manhattan.

A Greyhound spokesperson said, "We are fully cooperating with authorities on this active investigation."

"As it is ongoing, we cannot provide further comment at this time," the spokesperson said.

The bus angle in the probe was disclosed hours after the New York Police Department released two new photos showing what an NYPD spokesperson called a "person of interest" who is "wanted for questions in connection with the shooting" of Thompson on Wednesday morning.

The images were captured by cameras at a hostel on Manhattan's Upper West Side.

"The New York City Police Department is asking for the public's assistance in identifying the individual depicted in the newly attached media wanted for questioning in connection with the below listed homicide," the NYPD's media affairs office said in a statement.

Investigators were at the hostel, HI New York City, on Thursday.

"We are fully cooperating with the NYPD and, as this is an active investigation, cannot comment at this time," a spokeswoman for Hostelling International USA, which operates the hostel, told NBC News.

UnitedHealth Group, in a new statement Thursday night, said, "While our hearts are broken, we have been touched by the huge outpouring of kindness and support in the hours since this horrific crime took place."

"So many patients, consumers, health care professionals, associations, government officials and other caring people have taken time out of their day to reach out. We are thankful, even as we grieve," the company said. "Our priorities are, first and foremost, supporting Brian's family; ensuring the safety of our employees; and working with law enforcement to bring the perpetrator to justice." 

A statement taped to the door of a Thompson family home in Minnesota on Thursday said, "We are shattered to hear about the senseless killing of our beloved Brian."

"Brian was an incredibly loving, generous, talented man who truly lived life to the fullest and touched so many lives," the statement said. "Most importantly, Brian was an incredibly loving father to our two sons and will be greatly missed. We appreciate your condolences and request complete privacy as our family moves through this difficult time."

Police on Wednesday released a video and still photos of Thompson's slaying, which showed the masked gunman shooting at the CEO, whose company is the largest private payer of health insurance benefits in the United States.

The shooter, who was wearing a backpack, fled the scene and got on a bicycle that he rode into nearby Central Park.

The NYPD also Wednesday had released surveillance photos from a nearby Starbucks store that showed the suspected shooter, who was wearing a mask or neck gaiter over his face at the time.

A $10,000 reward has been posted by the NYPD and Crime Stoppers for information leading to the arrest and conviction of the person responsible for killing Thompson.