Yes, we pray for our enemy so that God will bless them. People who kill are in worse situation than those who do not. Do not think that their lives are joyful and easy. Therefore they need God’s mercy more than us.
Death does not defeat Christians nor are Christians afraid of death. The earth has been flooded with the blood of Christian martyrs since the inception of Christianity and it is not going to stop until God’s kingdom will be done on earth as it is in heaven.
It is just that while on earth we Christians should make the most of it to bring the Gospels to people who have not heard of them and living by examples so that they know we are Christians by our faith and our love.