December is always a tough month in Argentina. I always insist to my family to not visit for Christmas, but they did again this year.
Keep in mind that after the holidays no one wants to cause any trouble and everyone goes on vacation, etc and things calm down.
I also think there is a lot of "fanning the flames": you say there will be riots and then riots happen because everyone assumes they will happen.
I was listening to the Clarin radio today and they actually have a micro-spot that (not sure how to say it in English, is is 5 seconds of music that separates one segment for another) that says "the appocolypse is here!"
So people begin to believe it and then act on it.