MADRID—Spanish police on Monday said a teenager had allegedly killed a teacher in Barcelona with a crossbow and wounded four others, in a rare incident of school violence in Spain.

A Catalan police spokesman said the suspect is younger than 14, so Spanish law precludes authorities from providing any specific information about him, including age or name. Local media said the suspect is a 13-year old who is a student of the Joan Fuster high school where the incident took place.