( Spoilers may be in this thread ) I have the PC version of Skyrim.

I travel to Northwatch Keep, in search of Thorald Gray-Mane. The guard tells me to keep out so I go behind a rock and sneak-arrow him a few times, killing him. The guard does not react; I remain completely hidden the whole time. He just stands there and allows himself to be killed. I bristle a few other Northwatch Guards with arrows, sneaking, mainly, when I notice they do not fight back unless I'm in the fort. As soon as I left the fort, they lowered their weapons and walked on as if nothing happened. From there, I can shoot them dead and they do not fight back at all, or wonder who is doing the shooting. As I do this, my arrow and bowstring suddenly turn invisible. I continue shooting even with the invisible arrow when Skyrim crashes altogether. I restarted and tried again. The same thing happened.

What is up with this? Does this occur at other locations, or only Northwatch Keep? Have other players had this problem?