What do I do?

I feel like a lot of us do, and it depends on how they come to you...
Are you thinking of killing when your angry at a particular person? I bet this is more common than people think.
Or is it sort of out of the blue, your zoning out while sitting outside and you see someone walk by and wonder what it would be like to kill them?
I've thought both and I admit I am a weird person but I wouldn't ever act on the urges, and I know that.
If you've drawn up the plans to, thought about how to and how to cover it up and so on... I'd say that's getting to the same level of worry as when someone is writing out a suicide note and planning their death. If it's to that point and there is a part of you that doesn't want to go through with that, you should find a professional to talk too. Ask them to help you with it, explain how you want to feel normal and good!
Good luck!

I am a therapist in MD but you don't give a lot of important details. We all have inapppropriate thoughts it's a matter of degree. We might say "I could just kill him right nolw" But you would know if they are thoughts that you feel you will act on or if you just are angry. We all think things we don't do. Channel this into energy put into other things. It doesn't make you weird or dangerous If they are really serious then seek help