Had a crazy dream about an ex?

Last night I had a dream about an ex-boyfriend I dated almost two years ago. In this dream, I was dating my ex until we broke up. Then he started dating someone else. He ending up getting killed by someone at school. Later he reappeared as a ghost and only I could see him. Then his ex girlfriend said she could see him too. At the end of the dream, he saud he loved me and he went away. Can someone tell me what this dream means?