Ofcourse you can kill him, but you will get a mark. But if you wait for Law arrive, the thief can run away. Id just kill him inside my own house and loot all what i can.
I didn't mean not to give you an answer, it's just not mine to give.
I would lock the door and have some fun calling for help. If the robber kills you while in your own house there will be no way for them to escape, take that into your advantage.
Could the rules include something for this case in specific?
It avoids whining and time wasting for everyone.
In my opinion, i have to say these new rules have too many leaks... I should be done something like a FAQ or GM´s should specify them more... I see a lot of whinning comming...