On April 7, 2017 a truck crashed into a Stockholm department story killing 4 people and injuring 10. The BBC talks about this device:
Police say it is too early to tell what the "technical device" in the lorry was - only that "it should not be there".In discussing whether or not there had been further terrorist attacks in Sweden this justifies a statement I make a few weeks ago here:
"I cannot say at this stage that this is a bomb or some sort of flammable material," Mr Eliasson said.
"We are doing a technical investigation."
Sweden has taken in nearly 200,000 refugees and migrants in recent years - more per capita than any other European country.Bringing in people from war-torn societies can become a recipe for disaster without a doubt.
However, there was a drop in numbers last year after the country introduced new border checks.
Separately, Sweden is believed to have the highest number of Islamic State group fighters per capita in Europe.
About 140 of the 300 who went to Syria and Iraq have since returned, leaving the authorities to grapple with how best to reintegrate them into society.