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."

The gunman’s motive hadn’t been determined by early Wednesday as the Scandinavian nation — where gun violence at schools is very rare — reeled from an attack.

Swedish police confirm around 10 people were killed at a school for adults on the outskirts of Stockholm. The gunman is believed to be among the dead.