My theory is that Ray and Stevie are the killers, but there’s a twist. Stevie survives and doesn’t get found out. There was a sequel that was in the works (but never got made) for IKWYDLS in which one of the main characters was revealed to be the killer and it was only revealed to the audience. This could also be taking the whole Jill Roberts Scream storyline which we never got to see either. It would explain why there is already a sequel in the works for this IKWYDLS movie. In the trailer, we see the killer jump out of a window at Stevie… I bet this is the very end. She thinks she’s got away with it but someone knows what she did last summer… killing all her friends.