Sad to see so many people here in the comments jump the gun and think of Russia.

Some local context: Today is "prinsjesdag" when the budget is announced. Protests are common, particularly when sensitive decisions are made. There are multiple organized protest movements in the country that have used physical force in the past and some of them had announced protests for today.

Could it be Russia? Yes. But local protests seem significantly more likely. Moreover, if I were Putin I wouldn't expose my foreign agents this physically. I would use them in much more insidious ways such as actually starting or supporting these protest movements. In a similar vein: Could any shooting in the US be caused by foreign agents? Maybe. But usually there is a much simpler explanation; guns and bitterness.