Killing enemies with one attack does not make their friends hostile.
It happened to me in the goblin fortress and in the house with the cultists near the injured tiefling. I killed a goblin/cultist with a single melee sneak attack from stealth when they were relatively far away from others. When I injure them I start combat with everyone nearby, when I one shot them nothing happens.
Not sure if this is a bug or not, I just want to mention it. You could argue that they scream when you injure them but one shotting them kills them silently.
Prof. Dr. Dr. Mad S. Tist
World leading expert of artificial stupidity. Because there are too many people who work on artificial intelligence already
Prof. Dr. Dr. Mad S. Tist 
