(Reuters) - Authorities were seeking a motive on Saturday as to why a high school student in the United States' Washington state shot dead a female classmate and wounded four others in a campus cafeteria before killing himself. The shooter, a homecoming prince at Marysville-Pilchuck High School north of Seattle, took his own life as his classmates fled to safety. The incident was the latest in a series of deadly shooting rampages at U.S.