Another important point. And again, not knowing COD and the autopsy finds it is only everyone's guess, if they were possibly showing defensive wounds or not for example. Even if at some point the life of the first victim was taken, the other victim must have fought in one way or the other.
Libby was a math whiz according to statements of family and friends, she must have been fast to thinking. She has also participated in at least one self defense course as stated in MSM. According to LE Libby had the "presence of mind" to engage the video function on her cell phone. She was a fast thinker IMO. If Abby was taken out first, Libby would have acted in some way. If Libby had been taken out first, I have no idea, if Abby would have known what to do or not. In any case, chances are fifty fifty, that at least one of the victims would have fought. And nobody heard or saw anything, that we know of (!).
Why not? Either nobody was close enough to hear or see anything, or the killer was known to Abby and Libby IMO. But if the killer was known to Abby and Libby, why did they film him? Perhaps he was just in the picture and the point is, that Libby had actual audio in addition.
The audio part may be the most important clue combined with any additional evidence, if they have any. Imagine for a moment the killer was indeed known to the girls, who is to say he hadn't been around on the trails (from a far) and the girls were becoming suspicious of him? If he was differently dressed or concealed himself (glasses?), they would not necessarily recognize him. Libby may have even texted someone (friends? family?) to get picked up earlier due to that suspicious person. See that? So in the end, it was the "suspicious" POI/BG, who killed them and not a familiar person. JMO. Not saying that's what happened. Just trying to rattle minds.;--)
All IMO
-Nin