Whoever armed themselves with a Rambo style knife and travelled to that house, did so with the intention of killing those girls inside. I think Ethan may have been in the wrong place at the wrong time, and was likely attacked first, whilst he slept. He would be wounded before Xana could fully comprehend what was happening. We know she woke up, since reports say Xana had defense wounds and fought for her life. You would think a person may snap out of a psychotic episode after such a struggle, but clearly still enraged, the killdr walked the stairs and repeated the same horror in the 2nd bedroom. Attacking Kaylee as she slept, waking Maddie, who also tried to get her bearings, and fought for her life.
I believe this killer is slipping under the radar due to the fact, the police believe this monster to be a man. I would be zeroing in on ALL the girls who were known to these victims. Something motivated the killer to commit this deranged act. I think the motuve has more to do with jealousy than it being some sicko targeting these girls.. for what?. There was no sexual element involved. It was pure rage. I do hope a motive emerges soon, else this will end up being a cold case very soon.