Moments after Luigi Mangione was put in handcuffs at a Pennsylvania McDonald’s, a police officer searching his backpack found a loaded gun magazine wrapped in a pair of underwear. The discovery, recounted in court Monday as Mangione fights to exclude evidence from his state murder case in New York, convinced police in Altoona, Pennsylvania, that he was the man wanted for killing UnitedHealthcare CEO Brian Thompson in Manhattan five days earlier. Christy Wasser, a 19-year veteran of the Altoona police department, testified on the fourth day of a pretrial hearing as Mangione seeks to prevent prosecutors from using the magazine and other evidence she found in the bag, including a 9 mm handgun and a notebook that were located during a later search.