For what it's worth, I can tell you ( living in a neighbouring country and going very often to Spain ) that you really don't mess with the Spanish Police. Period.
As a rule of thumb one should remember not to mess with the police of countries where you have terrorism.
stuff like that will go on in most places just not as open as that.
in the uk i know of 2 instances of similair stuff like that happening one with a car and other other with a bike.
one ended in riots which spread country wide.