IMO, the timeline of the girls drop off time and agreed pick-up time is tight. They were not given a whole lot of time to be at the park. This had to happen fair quickly after they were dropped off.
I have wondered how this person was able to take control of both of them. I know the way they were killed or what injuries they sustained have not been released.
It does appear to me when the BG is walking, he has something bulky under his coat. I don’t believe they were shot, someone would have heard that. Did he use a stun gun? Whatever happened, had to be quick, I would think. I don’t think it would be that easy to overpower two teenage girls, without one being able to take off. It’s possible, with sheer fear coming over them, commanding them was enough.
Any thoughts on them being pushed off that bridge, then the BG going down to where they had landed?