Hi B. Life is a journey and once you're on it you experience different things, including dreams. I would class this dream as a recurring dream, and I believe that is to do with death. I suspect, like a lot of people you have a fear of death and I suspect that you have a greater fear of anything happening to your mother.
I believe that you will continue to have this dream until you learn the lesson it is trying to teach you. It is very difficult to analyse this dream as you are only experiencing some of it, as the end bit is missing and I believe that the next time you have this dream, realise it's a dream, stay calm and dont over react stay with it as the message of this dream is in the ending. Once you can stay with it until the end, you will not have it again.
Hope this helps.