Luigi Mangione pleaded not guilty to federal charges of stalking, a firearms offense and murder in the killing of UnitedHealthcare CEO Brian Thompson.

Luigi Mangione pleaded not guilty to federal charges in the killing of UnitedHealthcare CEO Brian Thompson. Prosecutors declared their intent to seek the death penalty.

Luigi Mangione pleaded not guilty Friday to stalking -- travel interstate commerce, stalking -- use of interstate facilities, murder through use of firearm and a firearm offense in the death of United Healthcare CEO Brian Thompson.