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 king and queen visited the scene of the tragic event that occurred on Tuesday and Swedish flags were flown at half-mast to honor the victims.

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.