Gotcha, and I thought and thought about it, and chased a lot of rabbits while doing so.
If it was a crime committed by someone with beef against the girls, I could fathom one guy on one side of the bridge herding them toward another one waiting on the other end. Without assistance, the retaliation murder angle doesn't make sense to me.
After all this time, though, there is no evidence of that, so I go back to to the random guy with little fear response who didn't know them, and stalked them down the bridge.
Appreciate your thoughts and hopefully the investigators will sort this out soon.