Bad business, anyone affected have my sympathies.
In case people didn't know, ISIS have taken responsibility for this horrible act.
There seems to be a lot of misconceptions in this thread, especially when it comes to ISIS and their intent. They [ISIS] have very clearly stated that their aim is to create black and white narrative, where Muslims are forced to choice their faith or the western world, and that these two things cannot co-exist.
Of course, this is utterly false, there are countless of examples of religions being functional and secularized in the west, Islam as well.
If the intent is to defeat ISIS, then force alone will not work. The west needs to find it's own counter-narrative that it can spin. Cracking down in Islam will only benefit ISIS and other fanatics.