A dreamer does not ordinarily dream of killing anyone or themselves. This is because there are motives for killing and they include manipulation, gains, stress, impaired judgment, injustice and etc.
If you dream of killing, it can mean you are under great stress. You feel that the person who is giving you stress is your enemy. Your natural instinct is to survive. Your stress in bigger than what you can normally tolerate. You feel so much pressure that you are considering to leave the situation/ place. If you stay, you have to fight the stress.