It's ignorant to jump to the conclusion that the violence in Paris was done by refugees. What possible reason would they have for attacking the people taking them in (other than ISIS operatives planted amongst the refugees?)
The people responsible for this attack are most likely French citizens. Paris has had a problem with poor, jobless, disenfranchised Muslim youth from N. Africa for a long, long time before this current refugee crisis started. I don't remember the exact number, but hundreds of them actually slipped out to Iraq and Syria to train with ISIS, and half of them came back to France! Apparently, the government has just been sitting and "watching" them. They need their own version of Gitmo...