What was supposed to be a routine walk in the park with your girlfriend Leah and your pomeranian Peaches quickly turns into disaster in the blink of an eye. A loose pitbull springs from the treeline, mauling your girlfriend's beloved dog to death, and you too pay the price while trying to force the dog away. You're bleeding out, in pain and helpless as you watch the beast maul your girlfriend, ripping her clothes and scratching her body. And then, in the heat of its rage upon seeing her exposed rear, it decides to assert its dominance.
The prompt is somewhat long. It might be best to paste it in segments rather than try to import it all at once. I tried to leave Leah's description somewhat vague. You can project any appearance you want on her and even change her name if you want.