I mean, we don't know anything for real, do we? That's kind of the point. Just because the last story is sort-of presented like the de-facto truth doesn't necessarily make it so. Adrian could have implicated himself when talking to Virginia not because that's what actually happened, but because he saw this as the best way to convince her to get him out of this mess.

Anyway, to answer your question, there is no deer involved in any of the accident scenes in the movie. The only deer we see is the one standing near the water.