They were dead, like in beetlejuice. But they didn't know it (no handbook for the recently deceased.) When they vanish, it's them crossing over to heaven or whatever, leaving purgatory and those trapped there.
Explains why there are no amimals or insects and even the weather is a paradox.
That's an interesting premise.
shareExcept the red head killed himself and the corpse didn't vanish. So why would a lifeless corpse and blood splatters cross over? Why would car keys cross over, but not the car wheel someone is holding? It just creates more questions.
That aside the disappointing ending is so vague/unfinished nearly anything is possible - like a bad murder mystery where you never find out who did it & can accuse everyone, but cannot prove anyone is guilty. Maybe the whole thing was just an advanced high tech computer simulation game with someone deleting the characters and specific objects (like car keys) and altering the world/weather for fun. Or some powerful unseen deity playing with mortal humans for fun.