Originally Posted by
Glorthindel
There was potential for a very interesting party dynamic here, but the Fighter blew it to defaulting to violence. A party are supposed to be, at best, a group of friends, at worst, a group of co-workers who tolerate each other. Interpersonal friction is certainly within the bounds of play, but violence is not; what friend group would survive one member outright attacking another? None, it is just utterly unreasonable. There were plenty of ways to play out the situation that didn't involve violence, but the fighters player stepped over the line.
Sure, the fighter has already broken the fellowship, but again, premeditated murder is not the solution to a disagreement. You could argue that the rogue saw the water incident as an attempt on his life, and a sign of escalation, and knew a more serious attempt on his life was only a matter of time, but still, why murder, and not just abandon the party in the night and make a new character? Either way, your characters membership is over (no-one is keeping someone in the party who will just outright murder a companion in the night, regardless of provocation), so taking the Fighter out first served no useful purpose.