What does it mean if you dream that a polar bear is trying to kill you?

I had a dream that a polar bear was chasing my ex husband and he got away and then the same polar bear was chasing me relentlessly and viciously. He wanted to kill me and I kept trying to get behind a door and get it barricaded but he was quick and I found myself in terror and having to push the door shut with all my strength. Any thoughts on this dream?