My childhood friend is in my head, its spiltting and it hurts. What is wrong with me?

I have a childhood friend who I loved as a kid. Eventually we grew apart but they(being gender neutral just in case) had been on my but that eventually faded as well.

Last year, I started seeing them around again. Thinking we could be friends again or simply keep in touch, I started talking with them and it went well but then they met someone. The last time we talked they said, "I have a good feeling about this and I want to make sure this works." And then they ghosted, my friendship was gone. I was deeply hurt but after a while I didn't think much of it and no longer felt anything for them. The time we were apart had changed them immensely. They became someone who i didn't they capable of being, in a bad way.

Last month, i heard they were getting married and my mind has been a chaotic storm tearing itself apart. I was feeling angry and depressed, and I don't why. I tried blocking it out and forgetting about them and it seemed to work, but here and now, I just left at the end of their wedding reception, barely holding my self, and now my mind is worse off then ever. I can't control it anymore, my tearing up, I want to burn the world, i want end myself. Words of hate, sadness, destruction, ending it all, and more like it wont leave me. My mind is flooded and split in three, Rage, Depression and a little tiny spec that is holding things together while putting on a mask so the world can't know what I'm thinking. I haven't told anyone this, this is my own problem, I'm not making it anyone else but I feel like I need to tell someone this, which is why I'm putting it on here. Typing this out has helped me a little.

To be clear, I DO NOT FEEL ANYTHING FOR THEM but my mind can't seem to understand that. They and I went down different paths in life. We probably wouldn't get along if we dated. So why am I like this? What is wrong with me?