You mentioned rule 3.6 but didnt say what rule 3.6 says
Rule 3.6 (Stay Alive) Clearly states Players must, at all times, do everything in their power to prevent and/or avoid their own death.
So,there was no threat to your life which makes u to prevent your death and defend your life. Even if you think about it,the guy you shot is the same as u,he is also walking with a gun in the forest but doesnt show an active threat.
And you got a warning from phoondos for rule 2.5 which states Players may not excessively impact the experience of others in a negative manner, unless the actions are a proportionate escalation of negative actions that have been performed against the original player. ...