Thanks everyone. I knew I could rely on you all for support.
My stepdad is just beside himself. She had a tendancy to chase cars but she never ever got close to them. And he wasn't even going fast at all, he said it happened so fast though. He was just testing out the car and she came out of nowhere, ran under the car and must have got herself stuck under the wheel. He's not even entirely sure. She got up at first so he went quickly to grab her and put her in the car and bring her to the emergency vet but she died within 10 seconds. She looked exactly like herself, no blood, anything, so we think she broke her back. A little blood spit out of her mouth when he picked her up and he said she just stared up at him with her eyes and she was just gone.
Omg, I'm crying again... I just can't believe she's gone.