What you remembered last night actually occurred. But you may not remember the events in a past life exactly the way they occurred in history. Your past is affected by who you are now. You r future and your past are not fixed, both can be changed. This is very hard to explain.
People are so accustomed to thinking of the past as being fixed, unchangeable.
It is not. You encountered your past last night and your past showed you that, under a different set of circumstances, you are quite capable of destroying life. Memories of your past lives are not a totally reliable way to study historical events but they can be quite useful in helping you to understand who you are now. Yes, but I don't like it. That memory means that I am still capable of being involved in a massacre.