To dream of killing someone... This is a dream that says a lot about your current state of mind. You are done. Fed up with more than you can take, and are ready to fight back. The mind seeks a way to show you that a person you killed in your dream is defeateable and you are very able to fight back and win. In your daily life you probably are experiencing huge pressures that are demanding too much out of your time, and you can't say NO! Saying no is what your mind is doing right now. It is telling you to stand up for yourself and face the person you are avoiding to fight.
Some interpretations say, killing someone in a dream is a sign of defeating the parts of your psyche that are toxic and need to be cut down. Pleasures and too much of postponing and of course, procrastinating is a sure bet here!
If you saw lots of blood around, while killing someone in your dream, then the thing that will be resolved is comming soon and you have to be prepared. Red blood singnifies a fast aproaching battle. Of course, there are some parts of your behavior that are not really needed to be destroyed. If you killed an animal in your dream, any kind of animal, then this is a sign that you trust more your logical mind now, instead of your animal inscinct.
Logical thinking is a priority now. This is alright for the time being, but don't forget your needs also. Need to rest, enjoy and be free. Animals don't pressure themselves beyond foraging for food. They use their time to rest and groom. Just be sure to take care of that animal sign you are deep down and the love will return back to you.
Killing a friend or a loved one in a dream is not a bad dream as it may seem to you right now. There is an old salvic saying that says "If you killed a friend, family member, or even a loved one in your dream, you've actually prolonged their lifetime"!
First of all you really love that person you killed. The mind wants you to show more love to them and not be so ambivalent and flat towards them recently. They also love you very much, but sometimes there are differences that are an obstacle between the two of you. These are the obstacles your mind sees and wants to kill in order for you to progress. This is the way of the subconscious...