I am, more and more, going back to my very first theory upon hearing of the murders. These girls were very likely, imho, killed by a group of young males in the area who were also off school that day. There was probably some kind of party out there, maybe starting overnight and lasting into the day. That might explain why there was a relatively larger group of individuals at the trailhead when the girls were first dropped off. The girls might have been out there looking for it. Once directed to it by NBG, they walked into a group that was out of hand, and what happened to them is what has happened to way too many other girls walking into similar situations. And, then they were killed.
Now, LE is faced with members in the community who don't want to "ruin" the lives of the perps, star athletes, etc.
I probably should have stuck with this theory from the get go, instead of going off on a tangent. But, it is what it is.
All just MOO, but I am becoming resigned to it.