As per my understanding, the people who @kobrakulsh has interviewed or did PLR, does not even have any characters of a serial killers. They were first victims and latter due to helplessness, they might tried to injure the other or to made an effort to put an end to their own suffering.
Real Serial killers will not have remorse and I believe they share their story of killing people and how they fantasises.
In fact Psycho killers have a way to manipulate us, if we were interviewing them. Which was originally reported by first psychologist in FBI who introduced criminal psychology in FBI. There are many cases.
In order to bypass this they have to be in semi sedative mode and do the regression, however when they realize their self it can lead to other characteristic. Because their subconscious and conscious are both one inside the other or inter linked.