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 shooter targeted a center that serves migrants seeking to integrate into a country that had already reversed its liberal migration policies.

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.

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 shooting occurred at a center for adult education in the city of Orebro. The suspect is believed to be among the dead, officials said.

"But this hate, it is coming from somewhere." A member of Kasselia's congregation, 29-year-old Salim Iskef, was among those murdered in Orebro on Tuesday in Sweden's first school shooting and the worst mass shooting in the country's history.

By Johan Ahlander OREBRO, Sweden (Reuters) - Ten years ago Salim Iskef, 29, fled the Islamic State and Syria to form a better, more secure life in Sweden, only to be gunned down this week in the worst mass-shooting in Swedish history.