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."

Sweden is reeling days after the country’s deadliest mass shooting left at least 11 people dead, including the gunman, as investigators Thursday continued to look into the shooter's motive. At least five people were seriously wounded in the violence at an adult education center west of Stockholm on Tuesday.

The authorities said that at least 11 people were killed and that the suspect was believed to be among the dead.