Mangione is awaiting state and federal murder trials in the killing of UnitedHealthcare CEO Brian Thompson. The criminal complaint against Anderson did not name the inmate, but a law enforcement official confirmed it was Mangione. Anderson is expected to appear in Brooklyn federal court on Thursday. Hours before Anderson’s arrest, the Manhattan district attorney's office sent a letter urging the judge in Mangione’s state case, Gregory Carro, to set a July 1 trial date. On Friday, Mangione will be in court for a conference in his federal case.