This section is from the book "The Psychology Of Dreams", by William S. Walsh. Also available from Amazon: The Psychology of Dreams.
In nightmare the individual seems as if about to be done to death by some fiend, or to be killed in some other way; these dreams are often accompanied by emotion. In other dreams the dreamer acts the part of a murderer or that of the murdered without experiencing emotion of any kind. There may be a desire to run away, but apart from fear of capture there is no other emotion, as regret.
Dreams of murder are explained in many ways. Some writers attribute them to digestive disturbances, respiratory, and cardiac discomforts, which produce a profound impression on sleeping consciousness. The mind attempts to explain the impression, and from its magnitude concludes that something very serious has happened. The most serious ill that could befall one is being murdered, or being a murderer, and this is the conclusion that sleeping consciousness arrives at. The acceleration of the heart and respiratory rates suggests flight, and one flees only when in danger. This also suggests the idea of murder. On the other hand, dreams of murder are sometimes explained by symbolism; this subject will receive more attention in the section on nightmare. The morality of these and other dreams has already been discussed.