Air Force Staff Sgt . David was shot with 5 bullets in Ciudad Juarez . Investigators recovered more than 30 shells from the scene . Gunmen claimed to have targeted the victims , Mexican media says . Juarez is considered off - limits for the U.S. military because of the violence .
Air Force Staff Sgt . David was shot with 5 bullets in Ciudad Juarez . Gunmen claimed to have targeted the victims , Mexican media says . Juarez is considered off - limits for the U.S. military because of the violence .