What the Hell is going on? Please explain this behaviour.

Please somebody explain me this totally weird behaviour:

I was having a very nice and lighthearted romantic story when suddenly out of nowhere and without any warning a tall person in Metal Armor appeared and grabbed the Woman in my Story by her neck, broke her neck and bones and threw her dead to the ground!!

Why in the hell did that happen? Thats not a minor error thats a huge problem in the AI isnt it?