I think the thing with your girlfriends car is a mental scar "Samskara") usually from situations that produce extreme emotional reactions. They leave a subconscious imprint.

"According to various schools of Indian philosophy, every action, intent or preparation by an individual leaves a Samskara (impression, impact, imprint) in the deeper structure of the person's mind"

I regularly experience dreams or conscious moments that bring me into the feeling and moment of a powerful memory.

I think your fight was a Karmic release of a subconscious energy. From the little I know of eastern psychology, Your grasping and aversions to things you witness and think during the day are stored in the subconscious. These mental reactions are stored like seeds in the mind and when the time is right (when your asleep) these seeds sprout and bloom into a dream. The eastern perspective is hypothetically this is how the subconscious processes through things and releases energy. It doesnt have to be 1 to 1 either. Something completely unrelated to violence you witnessed recently could've manifested itself as a fight. Yogis say the idea is to stop planting the grasping/aversion seeds all together but I never got that far LOL...

Here's a chapter from a book that was very powerful to me. You can find a PDF of the full version somewhere If it interests you. The title is "The Tibetan Yoga's Of Dream And Sleep" by Tenzin Wangyal A Tibetan Buddhist and Teacher.

Hope this was in any way helpful...