The "miracle" of the MacDonald family is that there were four different blood types. A, B, AB and O. This was what convinced me that Jeff murdered his family, because the blood tells the story. Jeff is B and Collette is A. Collette's blood starts dripping in the hallway, near Kimberley's. In fact, there is quite a bit of blood of both of their blood in the hallway. Then Kimberley's blood follows her into her bedroom, where is spatters all over her bedroom. Collette's blood is in her bedroom as well, but NOT much of Jeff's blood and not any of Kristen's. Then, Collette's blood is in Kristen's bedroom, as she runs in there to save her only living child. Jeff probably finished killing her there, as there is a great deal of Collette's blood there. Was Kristen awakened? We will never know.
We do know Collette's blood trails from Kristen's room back to the master bedroom, where there is a great deal of Colette's blood and a little bit of Jeff's blood and some of Kimberley's blood, probably transferred from Collette.
Finally, Kristen's blood is mostly contained in her room because her daddy killed her in there, most likely as he held her on his lap. She was, after all, his favorite child. She was the tomboy, the one who didn't trap him into marrying Collette. The one who looked more like him and who acted more like him. The one he intentionally killed. If any of the murders bothers him at night, this is the one that likely haunts him.
But he did it. The blood tells the story. Jeff's blood--and ONLY Jeff's blood--is in the bathroom sink. Where he stabbed himself after finishing off his youngest daughter so he could, hopefully, keep his career.
Honestly? I believe he accidentally killed Kimberley and that started this whole awful string of events. But I DO believe he intentionally killed Kristen and Collette to stage it.