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.

But the scale of the loss of life means the public and politicians want answers from the police now. More than 100 specialist officers are involved, on a local, regional and national level. Unconfirmed reports in the Swedish media say the gunman was a 35-year-old local man who legally owned a gun.

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."