Luigi Mangione has admitted to killing UnitedHealthcare CEO Brian Thompson after pleading guilty to federal charges of interstate stalking resulting in death.

Luigi Mangione admitted on Friday to gunning down UnitedHealthCare chief executive Brian Thompson, as he appeared in US federal court to change his plea to guilty.

Mangione, 28, read a statement in court in which he described tracking Thompson, 50, to the conference in Midtown Manhattan and shooting him with a 3D-printed gun equipped with a silencer.