Lawyers for Luigi Mangione are engaged in plea negotiations with federal prosecutors in the killing of UnitedHealthcare Chief Executive Officer Brian Thompson, but those talks have stalled.Mangione faces state murder charges and federal interstate stalking counts tied to the December 4, 2024, shooting in Manhattan; prosecutors say he stalked Brian Thompson online and crossed state lines to carry out the attack, and early terrorism-related counts were dismissed.He has pleaded not guilty, withdrew an immediate psychiatric defense, was arrested in Pennsylvania, and faces trials in state court in September and in federal court in January while juror selection moves forward.