When you see a killer in your dreams, it is an indication of your own anxieties in the waking life. Are you mishandling work related tasks that you feel threatened about if it was exposed? There are certain things you would rather have remain hidden.
The fear of being exposed or revealed creates the killer character in your dreams. The way you handle this dream is to thoroughly go through all the things that trouble you in real life, and come up with a solution for each.