When you say Eastern Orthodoxy, are you referring to the Eastern sui iuris rites of the Catholic Church, or to the Orthodox Church that is not in full communion with the Catholic Church?
If you are talking of the former, could you kindly specify where is this taught? I am only familiar with the Catechism of the Catholic Church - which I believe applies to the Eastern rites as well.
If we are talking of the latter, then I see no point in further expanding the argument, for all communities that separated themselves from the Catholic Church have developed their own doctrines and teachings outside of Sacred Tradition. I only focus on what our teacher, the Magisterium, says on these matters.
The Church teaches that if you are in danger of death, or an innocent is, then your life and the life of the innocent(s) are to be preserved even at the cost of the life of the attacker. I would personally still confess this, simply because I cannot be fully sure that in a way or another I have not offended God, but I would not consider myself guilty of mortal sin.