I am so sorry about your dog!
But it sounds as if even if you had gotten her into the vet in time there would not be anything successful that could have been done for her. I am just speculating but she may have actually broken her back, or alternatively an embolus (a blood clot or other blood blockage) could have lodged in her brain or in her spine near her brain and caused a terminal blockage, or infarct, (something similar to a deadly stroke in a human).
Jaybay, Thanks again for your help!
She may have seriously injured her spine, like a ruptured disc or worse. I suggest you try to find a 24 hour emergency vet somewhere near you. They aren't always easy to find, so try the internet first as a search. Keep him as motionless as you can so as not to make the injury worse.
My mother-in-law's chihuahua did the same thing simply jumping out of her sedan. The poor little guy landed, and the whole back end just fell down. Turned out he broke his back and had to be put down.
She ended up having a few seizures and died 4 hrs later. Our nearest 24 hr vet was 2.5 hr drive from home.
Thanks anyways
Shell
Oh I am so sorry! I guess the only good thing is that she took the decision out of your hands and didn't linger and suffer for too long. :-(