Better still, if you use ability that causes bleed, you can kill an NPC without any recurse (assuming the first or second hit + bleed kills them) even when several people are watching. Killed Esmeralda that way and could loot her ENTIRE STORE inventory (which she dropped as well by the way.. wee ,p). (Witch ability , Shred them or what it's called ,p)
Apparently such 1 shot kills skip the trigger for the reaction script, and thus nobody reacts.