Walpurgis

The attack came on the eve of the Walpurgis spring festival, when large crowds are expected to descend on the streets of Uppsala, a university town north of Stockholm.

The incident happened on the eve of the Walpurgis spring festival, which brings large crowds onto the streets of Uppsala, which is located north of the capital Stockholm, and known for its university.

Tens of thousands of people typically travel to the Swedish city of Lund in celebration of Walpurgis Night, a festival that also sees parties and bonfires scattered across Europe.

Walpurgis Night, which runs from April 30 to the evening of May 1, dates back to pagan celebrations of spring.

Tens of thousands of people usually descend on southern city to celebrate Walpurgis Night, which is marked across Scandinavia.