So Piper is the kid of Brandon James and one of the killers. I've thought this for the past four or five episodes now. She appeared from nowhere and inserted herself into the investigation. Plus her whole thing about how she didn't have a dad and encouraging uh... the lead girl--Emma! To make amends with her dad because second chances and all that shit from last week.
It threw me a little when they went to Brandon's mom's house and the mom said that it was a boy that visited her and that it was Brandon's kid. I'm thinking one of two things: Piper is transgender or just pretending to be a boy. If this is the case I'm betting the Scream team is PISSED that Pretty Little Liars already went there last week, LOL.
OR Piper sent Jake to visit, which is who I think the second killer is. I think he's a bit of a mashup of Billy & Stu from the original movie and maybe Mickey from Scream 2--someone in it for the thrill (he's a spoiled, rich white kid, after all), someone who wants to get the girl [the bitchy blonde one I can't remember the name of], and someone who's tech savvy enough with some prompting from Piper).
Kieran is a red herring, as is Branson. Just a bunch of shoddy storytelling on the parts of the writers to make them have just a touch of guilt on them. Branson conveniently has to keep quiet because his lawyer told him to when he was talking with Emma and Kieran just happened to meet Bella Thorne (seriously, where did she ever come from because she seems like she's everywhere without having done anything. And she's super wooden in RL from what I've seen at award shows) at a bar just before she died.
So Piper is doing this because she wants revenge on the town that vilified her father, and the family she never got, the sister who took the place she thinks she deserved, the mother who gave her away, etc. Jake is doing this because he's bored and wants to be taken seriously.
All this said I like the show, actually. I'm glad it's only 10 episodes, though, because another two or three trying to stretch this shit out would be torture. I guess I'll find out next week if my theories are true on who the killers are.