A photo of a New York Starbucks may hold the key to finding Brian Thompson's killer

New York police are using facial recognition technology and a discarded cell phone to identify and track down the killer of a top health official.

UnitedHealthcare CEO Brian Thompson, 50, was shot in the back Wednesday morning outside the Hilton Hotel in Midtown Manhattan.

The assailant fled the scene without taking Thompson's property. Police believe Thompson was targeted in a planned murder.

They focused on surveillance footage taken at the Starbucks branch shortly before the shooting.

Here's what we know about the suspect and the investigation.

The shooting happened around 06:45 EST (11:45 GMT) in a busy area of ​​Manhattan near Times Square and Central Park. Thompson was scheduled to speak at an investor conference later in the day.

According to police, the suspect – who was wearing a black mask and a light brown or cream colored jacket – was seen waiting for Thompson for five minutes outside the Hilton hotel where he was expected to speak.

Thompson, who arrived on foot, was shot in the back and leg, and was later pronounced dead at a local hospital.

New York Detective Chief Joseph Kenny revealed that the suspect's weapon appeared to be malfunctioning, but he was able to fix it quickly and continued shooting.

The video shows him fleeing the scene on foot; last seen in Central Park riding an electric bike.

So far, the investigation into Thompson's murder has focused on a few lines used by the police to identify the suspect.

Police said the suspect was photographed at a nearby Starbucks minutes before the shooting.

While he was hiding in the photo, police sources told CBS, the BBC's US partner, that the mask was pulled down enough to reveal his eyes and part of his nose.

For that, investigators use facial recognition software to try to find matches.

Additionally, police tested three bullet casings and three bullets found at the crime scene for DNA.

The words “deny,” “protect” and “demolish” were found on the boxes, police sources told ABC News.

A mobile phone was found on the road near the escape route of the suspect. Police say they are “working” on the phone.

Investigators also said they will search Thompson's room at the Marriott, which is just down the street from where the incident happened.

Investigators have not yet found a reason for his murder, although the police noticed that the suspect fled without taking Thompson's property.

In an interview with MSNBC, Thompson's wife said “there have been threats” made against him in the past, although she could not provide details.

“I just know that he said that someone was threatening him,” he said.

According to police in Thompson's hometown of Maple Grove, Minnesota, there had previously been one suspicious incident at his home in 2018.

The incident was cleared with no criminal activity found. No further details were provided.