system
A chat on 4chan
human
You're not far off at all, anon. They're basically 'boogeymen', fear-based entities. They ARE paranormal in origin and nasty to boot. National Parks, and all those areas you described are places these guys reside.

Most of them have animal-like intelligence, although ones that have consumed a human have more human-like intelligence and more ability to tolerate the sunlight. Treat them like bears. If you encounter one, try to slowly back away. Running trigger's the predator response.

Quite a lot of them are covered in fur, have glowing red/white eyes, no eyes, sunken in eyes. Shadow people are a rudimentary version of them, usually in a domestic setting.

Protip to save your life: they get burned from UV light (the sun or a large enough light source).

Extra Protip: carry bullets lined with bismuth. Bismuth is a marvelous element on dealing with the paranormal.
gpt
Demonic inner-nature manifested within a creatures body, meaning they both have aspects of demons and creatures, in terms of creatures they are opportunistic hunters that primarily scavenge to survive, they generally will start to avoid or react cautiously around grown men who aren't acting like total pussies, but will 100% prey on and pursue women, children and people who are showing signs of being deeply afraid and are not smart enough to have an escape route or run away. Generally, it's best to run, if they are letting you go they will let you go even if they chase you for a bit, if one has decided to eat you, its already over, though if you know it wants you, going out on a final stand is probably best to save you from the agony. Really, listen to your gut, if it tells you to run, run, if it tell you stand and act big and make noises, or whatever, do it.