I went in Vault 3 and spoke to the woman guarding the place. I passed the check and she used the radio to tell the others to let me pass. I changed my mind right after that and took her down with my riot shotgun. I ended up killing everyone in the first level. When I went to the level with Gun-Runner, the guards were grumpy but not hostile. So I went to speak to Gun-Runner and offered to sell him something and did not sell anything. He thanked me for trading with him. I picked up the quest items for the Brotherhood in a locker in his room. Still no hostility from the fiends. Must be the chems. I would have thought since I attacked and killed everyone in the first level that I would not be welcome in the other levels. When I went back to the first level the respawned guards were not hostile even though the dead fiends were littered about. Either they are very forgiving or really dumb from the chem abuse. I plan on going back and freeing the NCR guy that is trapped there and helping him out. I was told this vault was buggy.