Everyone is interpreting this as a budding PvP. But was it really? I've been in several scenarios where a new character is introduced to the party midstream and gets a weapon pointed at him until we roleplay out how that new guy establishes who he is and why he's there. In none of these were the other players ACTUALLY going to attack the new character. They were roleplaying wariness on the part of their characters with the implicit understanding we're acting out a scene that needs to end in the new guy joining the group.
I guess I'd need to know if the player in question was actually going to shoot at the new guy (which may or may not be unacceptable depending on the gaming group), or if he was roleplaying in a way that seemed consistent with how villainous characters meet and negotiate alliances with one another. Pointing a crossbow and firing it are not the same thing.