Yes, I think this fox could have killed a new fawn. It was a big fox. If the fox has a den close, it is the same location as the momma deer has been hanging around bleeting and looking for its baby. Deer drop the fawn then leave it, only coming back to it a couple times a day to nurse it. The fawn has no scent when it is born, so the mama leaves it so predators don't come to her scent and get the helpless baby.