My 1 Year Old Dog Died All of a Sudden?

I lost my little girl this week. She was a breed mix very cute. I rescued her little over 2 month ago. She was by my side all the time. We the other day she got up eat, we played and all of a sudden she started seizuring and they were strong. She had 4 hard ones before we got to the vets. 6 hrs later vet said I had to make a decision the outcome wouldn't be good if they continued she was not responding to any medication. She had no signs of anything. We played like we always do. I just don't understand why why this happened. I just can't believe something so small and cute could put a bent in your home after 60 plus days. We will never know why either. She was only 1 1/2 year old. We were giving her a life and know my heart is broken.