I’m wondering if the guy is even telling the truth about the girl (Kifer) laughing at him after already getting shot. If so - sounds like all sorts of crazy going on.
It seems unlikely that the girl laughed after seeing her boyfriend killed, finished off, and placed onto a tarp, and herself being wounded and lying in the killer’s basement.
It isn’t unlikely that he perceived her sneering at him, or even laughing at him though.
I’m kind of curious about the whole basement thing, and the separate appearances of the girl heading for the basement after the multiple shootings of her boyfriend and in effect creating another execution set up, I wonder how they really ended up in the basement.