That low speed and minimal injury count suggests more of a medical issue or distracted driving, or somebody coming around a corner and encountering a crowd in a road, trying to stop. I would imagine a deliberate attack would have involved a greater speed and numerous deaths and injuries.
My first thought was that this could be an accident. But there is nothing mentioned about the suspect, which is typical in a terrorist attack. So I thought it was worth a look.
Plus, from the article:
A spokesman for Sweden’s police service said children “threw themselves” out of the way of the car, which appeared to have aimed directly for the group of 100 people.
He said: “The car accelerated into the group of students and teachers.
“The car increased speed and drove straight towards them.”