Police have released two new images of a suspect in the hunt for the gunman who killed a health insurance executive in New York.

UnitedHealthcare CEO Brian Thompson, 50, was shot in the back on his way to a conference on Wednesday in what police believe was a targeted attack.

On Saturday, the city’s mayor, Eric Adams, said the “network is tightening” around the shooter, who has so far managed to elude police despite an extensive search and the use of facial recognition technology.

The FBI is offering a $50,000 (£39,000) reward for information leading to the arrest of the suspect.

The latest images of the wanted man both come from a vehicle. In one, he is seen in the back of a taxi, wearing a hoodie and a disposable face covering.

In the second picture he can be seen outside the car, again wearing a face mask.

The new objection came as US media reported that a backpack found near the crime scene, believed to belong to the suspect, contained a Tommy Hilfiger jacket and paper money from the board game Monopoly.

Thompson, a 50-year-old father of two, was shot as he headed to an investor conference in midtown Manhattan where he was scheduled to speak later that day.

Police said the shooter first fled the scene on foot and then rode his bicycle toward Central Park.

The motive for the killing is still under investigation. Authorities have confirmed that bullet casings found near the victim’s body had the words “deny,” “defend” and “depose” written on them – language associated with critics of the U.S. private health insurance industry could be brought.

On Friday, a person familiar with the matter told CBS News, the BBC’s U.S. affiliate, that investigators believed the suspect was no longer in New York City and may have boarded a bus to Atlanta, Georgia.