oops i realised that she was killed by her daughter. since everyone who watches the video has to kill the person they love the most. and i believe they both have watched it
she died due to the hallucinations caused by the videotape. kyung ho is a hypnotist. he makes people who watch the video see a woman in white and go crazy.
kyung ho erased the memory of her dad, and nobody thought that this politician was a killer. so maybe kyung ho carried her body to the station. and then police found it there.
jaeyoung was kidnapped by the cult member.