The islamist attackers of Charlie Hebdo had obviously been trained and prepared to carry out their military-style raid against journalists in the middle of Paris. Such terrorists will always go against unarmed civilians.
As long as we as a society remain generally unarmed, we will suffer such attacks, and increasingly so, as these attacks prove to be highly efficient and successful. The gunmen will always have the element of surprise and there will never be sufficient police immediately around to stop them and make them lose the initiative fast enough. The police will always be late. The only person who could effectively put an end to such attack would be an armed victim.
Had some members of Charlie Hebdo been armed, then the attack would either not have occurred or it could very well have ended differently. Of course there is never a guarantee for such an outcome. What is certain however, is the outcome of such attack if none of the victims carries a firearm. The terrorists know that and they can proceed with the carnage as the proverbial fox in a henhouse.
The only thing that stops a bad guy with a gun is a good guy with a gun.