You don't know what you would do until it actually happens.
Obviously you should fight, and you can try to convince yourself that you would fight in this situation, that you are hypothetically brave,
but in reality but you might be paralyzed by fear or overcome by the instinct to run away.
However I must point out that parisians are much less brave than the average bear.
Their attitude to crime in general is to look the other way, wait it out, and hope they won't be the next victim.
If this happened in another country, somebody might have jumped on the attacker(s) when they were reloading.