The police responding to the attack encountered firing so intense that they struggled to tell how many gunmen were on the scene, an official said.

Sweden is reeling days after the country’s deadliest mass shooting left at least 11 people dead, including the gunman, as investigators Thursday continued to look into the shooter's motive. At least five people were seriously wounded in the violence at an adult education center west of Stockholm on Tuesday.

Salim Iskef, 29, fled the Islamic State and Syria to form a better, more secure life in Sweden, only to be gunned down this week in the worst mass-shooting in Swedish history.