Officials in Sweden have vowed to determine why a man killed 10 people, and apparently himself, in an unprecedented attack that's shaken their "society to its core."

A major police operation is underway in Örebro, Sweden, after five people were shot at an adult education centre. Armed police were scrambled to Risbergska School at lunchtime on Tuesday as terrified students hid under their desks and barricaded themselves in classrooms.