Snipped-
There were a few seasons still going on, rabbit, fox, coyote, and crow, AFAIK.
Landowners and lessees are not allowed to hunt year round, only during designated hunting seasons. However, landowners and lessees may kill nuisance animals year round. Fishing is a year round thing and a license isn't required for fishing on private land.
Seeing someone decked out in full camo, even carrying a weapon wouldn't seem out of the ordinary to me and likely any LE in the state of Indiana. Even after seasons end, people are still out putting up and taking down trail cameras, moving hunting blinds and stands, and scouting hunting areas. I generally carry a weapon when I'm out in the woods as a general precaution. I've never run into any aggressive predators, but I've known people who have. Also it's not uncommon to run into trespassers and you just never know their intentions.
I don't think he has to be a local and I don't think it would have required a lot of planning. Aside from showing up in a fairly unknown area, it doesn't take a real genius to get around in the woods. I do it all the time in places I've never been without prior knowledge in some huge wilderness areas without landmarks where everything looks the same. One walk to and across the bridge would be able to show most people what areas were visible from the trail and bridge and what areas were not and the fastest and/or easiest route to get from one to the other. It's not hard to see whether a creek is deep or shallow or if the terrain is too steep. I think all he needed was decent situational awareness and a vague sense of direction, although under that limited amount of area, it's not really required as your main landmark (the bridge) would be visible for quite some time. If he walks too far, he's going to be able to see houses/structures.
Anyone who has spent time in the woods would be at an advantage in that situation, not just limited to hunters.
How many cameras were in the area? I've never heard anything that would point to anyone avoiding them because they knew they were there, rather than there just weren't any around. Some of the businesses may have had them, but they were likely focused on the parking lot and/or around the business itself. I doubt there were many trail or traffic cameras around. Not very many people would be willing to leave a trail camera in a public area just because of the risk of theft. We've lost enough of them on private property.
I will not speculate on the reasoning or motive for the murders. People murder for all sorts of reasons and sometimes no apparent reason at all.
I'm not sure exactly what you're implying re: Libby running into something near the bridge and being persuaded to return it.