Luigi Mangione is believed to be a person of interest in last week's deadly shooting of UnitedHealthcare CEO Brian Thompson, police said Monday. The 26-year-old was arrested on firearms charges in Pennsylvania, where New York police detectives were heading to interview him amid a massive manhunt for the shooter.

The ghost gun allegedly in Luigi Mangione's possession when he was arrested has been matched to three shell casings recovered at the crime scene in New York.