The serial killer is driven to commit murder over and over again. Consider that in the world of dreams, a death is an act of sacrifice where something that no longer serves you is being released in order to make room for something new.
The element of murder means this transformation is happening because of some measure of choice.
The serial killer that lives inside your psyche is a beneficial archetype that, though it lives in the shadow, is ultimately a part of your long-range growth and expansion. Such an image might be very frightening in a dream, but it must be examined through the lens of the universal principles it is expressing.... Complete Dictionary of Dreams
For most people, dreaming about whales is a pleasant experience. These huge water dwelling mammals may be symbolic of the connection that exists between the unconscious and conscious mind. They may represent the dreamer’s level of awareness, perceptiveness, and intuition. Some think that they represent our emotional power or are messengers from the spiritual realms.
If the ocean waters were turbulent, and the whale in your dream was unpredictable or on the attack, considers the emotional environment in your every day life. Under such unpleasant dream circumstances, these large animals may represent overwhelming emotional or psychological issue and problem. See also: Dolphin... The Bedside Dream Dictionary