Austria came to a standstill on Wednesday to mourn victims of one of the worst outbreaks of violence in its modern history, as authorities search for clues to why a 21-year-old gunman shot dead 10 people at his former high school before killing himself.

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.

Officials in Austria say a school shooting has left at least 10 people dead in the European nation's second-largest city, Graz. The shooter is also dead.