If the killer targeted one or more of the victims, how did he know their movements? How did he know they were home, or even coming home? Especially if the intended target was Kaylee?
It doesn't seem likely he could be following them because they traveled in a car. Was he really waiting for hours in the woods, in the freezing cold, with no phone to keep him occupied? Risking someone seeing him? How else would he know when they got home?
Unless he was already with K&M at the food truck and knew their destination when they left, OR was with X&E and knew their destination and time of departure, OR he was watching the house. If he was watching the house, I posit that he was watching from inside somewhere. I don't think he was sitting in the frigid trees waiting.
I think the killer either lived within sight of the house and watched from home, or he crossed paths with the victims either at the food truck or wherever X&E were last (frat party?) and knew precisely when the victims left for home.