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.

Ismail Moradi, 16, would normally be carrying his textbooks into school. But on Wednesday he was clutching a bunch of red flowers to lay in tribute to those murdered in Sweden's worst ever mass shooting. "I was shocked and didn't know if I wanted to come to school today after what happened so nearby" he explains to us.

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."