And amid the terror-come-trauma comes the bigger question - which reaction is the sensible one?
The French are emphatic. They attest a response of the "merciless" variety is the only possible riposte. Few would argue. And even those who did would have to concede such a response would be proportionate.
The subsequent commentary hasn't stopped flowing from politicians, retired military personnel, international law academics, current and ex-Presidents. All of it seems to stem from that very human desire to impose a measure of order over chaos. Yet, for whatever reason, it always comes across as futile.
Europe's security services, long deemed the most accomplished in the world, are now faced with a rapidly evolving terror. The real fear is that this terror is no longer the work of warped ideology alone, but instead a game of one-upmanship between Al Qaeda (responsible for Charlie Hebdo massacre) and IS (behind Friday's attacks). Both are competing for terror's market share.
The above question - au nom de quoi? - is thus a rhetorical one. The cruel players in this ghoulish theatre are like men in a dystopian blockbuster, "men who just want to watch the world burn".