Okay so here is my new theory on who the killers are and there is really only one part of it that I can't tie together. The main killer and Brandon James Daughter is Piper. Piper from the beginning has been the last person you would expect. She has been the one who Emma has opened up with some and she has been her guidance in a way but in doing so she has learned about the people closest to Emma. The biggest clue that is a huge part but was really easily looked over was that Piper tells Emma in once scene about how her father was murdered but she was to young to remember. Also this could explain Piper telling Emma it is Kieran just to make Emma go even more crazy.
So who is the second killer. Well my guess would be Noah or Jake. Noah because again you wouldn't really expect him but he has had an obsession with Brandon James so it wouldn't be weird for Piper to recruit him. The other is Jake because he should of died that one time but didn't which is fishy.
Finally my last Theory which is one that I just recently came up with after looking at the IMDb for scream. Mike Vaughn is listed as the actor who plays the killer. Maybe this means he is just the guy that behind the mask man that does all the stunts, or maybe this means none of the cast is the killer. After all Emma's mother did say she didn't think that Brandon was involved in the initially killings. So what if the person who committed all those murders years ago is the same person doing them now.
The biggest question that is still left to be answered however is why was Rachel murdered.
