What does this dream mean?

I dreamed that my sister was in my back yard playing with some neighborhood kids. It was kinda muddy and then it becomes extra muddy but their is no rain falling. I am looking out of my bedroom window at my sister. Then all of a sudden I can hear like a phorcious dog coming in the backyard, the dog appears but it doesn't have a threatning appearence it was like a yellow or tanish color shaggy dog but it sounded as if it was a pitbull or a large mastiff. Then the dog lunges toward my sister, then it decides to sit down next to her, I am screaming her name and she is screaming for help. It is as if she is trying to excape but she can't...I am also wanting to go down and help her but I can't seem to move. I tell my husband to go help her then he grabs the bat but he never appears in the backyard. Then all of a sudden the dog lunges at her and attacks her she stops screaming and when it moves she is still and her eyes are open. I awake and then I am to the dream again finding shes dead.