Austrian authorities were searching on Wednesday for answers to why a 21-year-old gunman shot dead 10 people in a rampage at his former high school before killing himself, one of the worst outbreaks of violence in the country's modern history.

Nine students were killed — six girls and three boys aged between 14 and 17, one with Polish citizenship — as well as a teacher, police said. Another 11 people were wounded.

A defense official said the man, 21, was turned down for military service after failing a psychological test. Investigators are asking how he passed another such test to obtain a gun permit.