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.

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.

Swedish police are still investigating the gunman's personal history and have not said the attack, which killed 11 people, was targeted. Hellen Werme, a 35-year-old trainee nurse, survived the shooting. She and her classmates locked themselves inside their classroom as the shooter prowled the corridors.