For what we are beiing told (as neighbouring country of France) The riot started with some guys who were on the run for the police and hide in a highvoltage cabine and got electrocuted. Now the people are angry because the police were folowing them (altough they deny this).

For what it's worth, If you behave you do not have to run for the police. Second if you hide in a cabin with high voltage / current you are just plain stupid.