First time I killed a shopkeeper, no guards came. I just did it as an experiment because I hated Oblivion's psychic guards and wanted to see if this was like that. Happy, I reloaded and continued just playing the game. About a week later, I was showing my brother the game and killed the same shopkeeper. This time it said I now have a 1000 gold bounty and all these guards started coming after me. I didn't understand. Today I played around with it some more. I kept attacking the same shopkeeper and reloading, and sometimes no guards would come, and sometimes guards would come. Every time I made sure there were no other witnesses in the building at the time. One time after the guards came, I killed all the guards and it said I had killed all witnesses and bounty was now removed. Then I left the building and everybody started attacking me. I don't get it.