Your question has 2 problems; how can creature created by God answer the hypotherical 'how would I act if I wasn't created be God'? The question doesn't make sense. The reason atheists and theists alike don't go around murdering people (for the most part) is because God has created us all with a sense of right and wrong, called the conscience. The real question you need to ask is where does the conscience come from? Evolution, or a higher being? Evolution can not account for it, at all.