A gunman opened fire at an adult education center in the Swedish city of Örebro on Tuesday, killing at least 10 people in what the country’s prime minister called the “worst mass shooting in Swedish history.

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.

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