How can I stop thinking about the death and killing of others?

You are thinking about death and killing is because you are reacting to a stimulus. First, you need to identify the ‘why’ so you can find out the ‘how to stop it’. The need for destruction comes from different sources, could be mere curiosity or perhaps a bad, terrible experience(s) that have affected you or the people you love. If you let those bad thoughts crawl and nest into your mind, they will become usual, normalizing any possible trauma. Eventually, if you constantly feed them with images, time, and emotions these will grow and consume you. Do not let these ideas take the best of you. You probably think those feelings have a form or a color, even a personality. Remember, they do not care about you. You have the power to make those thoughts stop and go away, you are in control.Sometimes, when we are in the middle of desperation we believe there is no way out, but this is false. There is always a solution, a way to clear your mind. It could surprise you how many people are willing to help you if you ask them for aid.