To dream about being murdered represents a side of yourself that you are letting go of. This could be a bad habit or an addiction that you have finally kicked or it could be an aspect of your personality that you have banished. It is generally a good omen that you have turned a corner and have put the past behind you.
If you dream that you have murdered someone else, this shows a deep seated resentment towards that person or even rage. Consider what aspects of their personality you really dislike, and then identify these traits within your own character. Are you angry at the other person or yourself?