U.S. Air Force Airman 1st Class Spencer Stone, one of three Americans that tackled a heavily armed gunman on a Paris-bound train, is greeted by well-wishers after arriving Thursday at Travis Air Force Base in Fairfield, Calif. Stone had been undergoing medical treatment in Germany since he and his two childhood friends, National Guardsman Alek Skarlatos and Sacramento college student Anthony Sadler, subdued the gunman on a passenger train Aug. 21.