ITA. IMO, it is far more likely that the perp drove as far off road as he safely could and walked the rest of the way in, carrying first one girl and then the other.
Because he is probably a local he knew the bodies likely wouldn't be found until hunting season and any trace evidence would be long gone. (Or so he hopes)
I also think we will be told that the bodies were not "placed" or laid out in any symbolic way, nor were they covered with anything to protect them from the elements.
If this scenario proves out, I would also guess family members, especially parents could be ruled out. Statistically even the most monstrous parents will cover or "swaddle" the children they have killed before leaving their bodies at a dump site. Swell, huh?
Anyhoo, its all MOO