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.

About 10 people including the gunman have been killed at an adult education center in what Sweden’s prime minister called the country’s “worst mass shooting.”

Swedish police confirm around 10 people were killed at a school for adults on the outskirts of Stockholm. The gunman is believed to be among the dead.