Recently i started a new game of skyrim (because i had to reinstall my os (vista home premium 32bit)) and i created a male nord and while i was doing the quest to get the golden claw i broke into moira's house and i killed a magic user (i assume moira) and i cleaned out her place (i took pretty much everything), then i resumed my quest, when i finished the quest i went back to riverwood to return the golden claw (i had to wait 7 gametime hours) i got ambushed by three nords who said their going to teach me a leason then they killed me, i went through that about three times until i ran into the river that runs by riverwood and the nords didn't follow me in and i was able to kill them with my hunting bow even though a couple of villigers attacked me and i killed them in self defence.
I looted the nords and got a contract off one of them and read it, it seems moira put a contract on me even though i think i killed her.

You broke into Anise's cabin and killed Anise. Moira is her sister (who magically knows the name of her sister's murderer!). You get a chance to meet her if you do Sanguine's quest.

However, NPCs (even dead ones) are known to send thugs after you for the weirdest things.

thanks for correcting me.

My Khajiit was kidnapped by Astrid and killed her. Now I kind of wish I hadn't because he's the awesomest assassin ever... he could have talked snark with that Dunmer, commiserated with Vereeza about how beastfolk are treated, and talked about blood and alchemy with Babette.