So, this is similar to chapter 1, this guy was actually already dead ever since the first page, but he never realized it. Hence his comment about the sudden chill. The family of 3 was already in a more advanced stage of undying, hence their corpse-like appearance to this guy.
Or perhaps like the cyclist in chapter 1, the camper actually already looks like a ghoul to living observers, which is why the version of himself that appeared in his selfie was a ghoul. Much like the cyclist and the driver from chapter 1 and the family of 3 in this chapter, he is doomed to eternally relive a ghostly version of his last moments. There is also what seems like a callback to another event in chapter 1 when he drives his car and encountered a fork in the road - the driver in chapter 1 was also warned by the monk to not go a certain direction (most likely they are supposed to find the ropeway, which is the only way for their restless spirits to ascend to the afterlife).
Makes me think of Futari Solo Camp - what if Gen never met Kana and this is sort of a "bad ending" for him lmao