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.”

The Orebro Police spokesperson confirmed that a major operation is underway at a school in Västhaga in Örebro and four people have been shot in the shooting.

Swedish police are investigating for a motive after a school shooting in the city of Örebro that has killed at least 10 people. NBC News’ Matt Bradley reports on what is known about the shooting.