Earlier tonight in the Islington area of London, four people were injured when a car plowed into them. After the collision, two men got out of the car and fled on foot. One man was arrested soon afterward. One knife was found in the car, and another on the pavement nearby. Police are saying that this event is not terrorism.
In view of what happened earlier this week on Westminster Bridge, I'd say that this incident being a copycat crime shouldn't yet be ruled out.