Swedish police say the shooter who killed 10 people in the country’s worst mass shooting was connected to the adult education center where he opened fire with at least one rifle-like weapon.

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.

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."