Update #4Today I finished adding some AI for the guards. If they hear your gun, they'll find the source of the sound and shoot you.
The rest of the NPCs are still oblivious to what's going on around them and will happily stand among pools of blood, so I'll have to implement some sort of generic system so that everyone can recognise dangerous situations and hide, attack or devise some kind of strategy depending on the tools they have.
My next goal is to create a small introductory map instead of the huge test mansion where I'm trying stuff out and start adding targets and way to accomplish them creatively.
Here's a gif of the guards avenging the death of their employer: