Witnesses who survived Sweden’s worst mass shooting have described horror and panic that gripped an adult education center west of Stockholm as the gunman killed at least 10 people.

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."

OREBRO, Sweden (AP) — Sweden’s worst mass shooting left at least 11 people dead, including the gunman, and at least five seriously wounded at an adult education center west of Stockholm. 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.