Luigi Mangione, charged with the second-degree murder of United Healthcare CEO Brian Thompson, has hired Karen Friedman Agnifilo, a former high-ranking prosecutor from the Manhattan District Attorney's Office, as his defense attorney. Mangione, arrested in Pennsylvania, is facing additional firearms charges and intends to plead not guilty to all charges. His defense may argue insanity, as suggested by his attorney's comments on CNN. The motive for the murder remains unclear, and Mangione is expected to appear in court in Pennsylvania, with potential extradition to New York. The Manhattan DA is preparing for both scenarios regarding extradition.