If the Traitor started to shot at you then you have every right to kill him. But if the T was killing someone else and you joined in to kill him, this would be RDM. But this does seem to be a mistake. Maybe you thought he was shooting you so you kill him and that is fair, as long as he started to shot directly at you.
Also some screen shots of logs would be nice. Good Luck.

If the Traitor started to shot at you then you have every right to kill him. But if the T was killing someone else and you joined in to kill him, this would be RDM. But this does seem to be a mistake. Maybe you thought he was shooting you so you kill him and that is fair, as long as he started to shot directly at you. Also some screen shots of logs would be nice. Good Luck.