My general understanding is that the totality of the site where the bodies were found as well as possible exits to and from the area would not require very intimate knowledge of the area. Rather, trespassing whether used to enter the area or in the form of straying from public trails is / was fairly common.
These circumstances and the relatively small size of the area would clearly support the perpetrator needing more than just casual, let alone theoretical knowledge of the area to commit the crime. They do not, in my opinion, however, suggest that very intimate knowledge is needed or that RL would need to be familiar with the perpetrator.
Rather, the required knowledge could have been gained by a fairly observant individual hanging out there as a youth or young adult or hiking the area over the course of a summer. Driving the road along the creek in conjunction with previous hiking or hanging out would probably help as well.
For example, as an outdoor oriented kid in my youth with a bicycle, I knew the local creeks, which alleys connected where, what woods had marked or unmarked trials through them and what fences had holes in them.
My knowledge of several areas did not stem from very intimate involvement with those different areas. Rather, it stemmed from being a local kid who had explored / messed around in those places a few times. I think it is the same situation with the murder regarding that area.
