Video of the gunman fleeing Wednesday’s shooting of UnitedHealthcare CEO Brian Thompson showed him riding through Central Park and later taking a taxi to a bus terminal, directly across from New Jersey, Chief of Detectives Joseph Kenny told CNN.

Police have video of the man entering the bus station but no video of him exiting, leading them to believe he left the city, Kenny said. “It’s a very busy bus terminal, we want to make sure we have the right bus. But we’re working through that right now, this is all new information,” he said.

Investigators also believe the shooter left his backpack in Central Park and were carrying out a massive sweep to find it, said police Commissioner Jessica Tisch.

The reason for the killing remains unknown. New York City police say evidence firmly points to it being a targeted attack.

The gunman who carried out the brazen ambush made sure to conceal his identity with a mask during the shooting yet left a trail of evidence in view of the nation’s biggest city and its network of security cameras.

A law enforcement official told The Associated Press on Friday that surveillance footage shows the suspect riding the subway and visiting establishments in Manhattan, providing more clues about his actions in the days before the ambush.

Investigators believe the suspect may have traveled to New York last month on a bus that originated in Atlanta, according to the law enforcement official, who was not authorized to discuss details of the ongoing investigation and spoke to the AP on condition of anonymity.

Once in New York, he appeared to pay with cash in any establishment where he was captured on camera, the official said.

Investigators have tested a discarded water bottle and protein bar wrapper in a hunt for his DNA. They also were trying to obtain additional information from a cellphone recovered from a pedestrian plaza where the gunman fled after shooting Thompson outside his company’s annual investor conference at a hotel just blocks from Radio City Music Hall and Rockefeller Center.

Police have released photos of the suspected shooter that were taken in the lobby of a hostel on Manhattan’s Upper West Side. The images, showing an unmasked man smiling in the lobby of the HI New York City hostel, add to a collection of photos and video circulated since the shooting — including footage of the attack itself, as well as images of the suspected gunman stopping at a Starbucks beforehand.

Surveillance images from the shooting show the man wearing a hooded jacket and a mask that concealed most of his face — a look that would not have attracted attention on a chilly morning.

Investigators have learned the man lowered his mask at the front desk of the hostel because he was flirting with the woman who checked him in, the law enforcement official told the AP, leading to a photo of his face. The woman told investigators that during that encounter she asked to see his smile and he pulled down his mask, the official said.

Investigators believe the suspect used a fake New Jersey identification card, the official said, when he checked in at the hostel, which has a café along with shared and private rooms and is blocks from Columbia University.

Investigators believe the shooter had at least some firearms training and experience with guns, the official said.

Security video shows the killer approaching Thompson from behind, firing several shots with a gun equipped with a silencer, barely pausing to clear a jam while the executive fell to the sidewalk.

The words “deny,” “defend” and “depose” were scrawled on the ammunition, two law enforcement officials told the AP on Thursday. The messages mirror the phrase “delay, deny, defend,” which is commonly used by lawyers and critics about insurers that delay payments, deny claims and defend their actions.

Thompson, a father of two sons who lived in a Minneapolis suburb, had been with Minnesota-based UnitedHealthcare since 2004 and served as CEO for more than three years.

The insurer’s parent company, UnitedHealth Group Inc., was holding its annual meeting in New York for investors. The company abruptly ended the conference after Thompson’s death.

UnitedHealth Group said it was focused on supporting Thompson’s family, ensuring the safety of employees and assisting investigators. “While our hearts are broken, we have been touched by the huge outpouring,” the company said.

UnitedHealthcare provides coverage for more than 49 million Americans. It manages health insurance coverage for employers and state and federally funded Medicaid programs.

In October, UnitedHealthcare was named along with Humana and CVS in a Senate report detailing how its denial rate for prior authorizations for some Medicare Advantage patients has surged in recent years.

The shooting has shaken corporate America and the health insurance industry in particular, causing companies to reevaluate security plans and delete photos of executives from their websites. A different Minnesota-based health care company said Friday it was temporarily closing its offices out of an abundance of caution, telling employees to work from home.