What does it mean when you dream that someone who is alive has died?

Dreams communicate through symbols and metaphors. In most instances, death appears in dreams as a symbol for change. It often represents the end of one stage of life and the beginning of a new phase. Dreams are also about the dreamer, so the person who died in the dream probably represents some aspect of the dreamer's own life that is coming to an end, such as graduation, the completion of a job or a move to a new locations.

Maybe they might have died that night or it might happen in a few years.