Has anyone watched Davidustin's Goatman myth video? At around 16 minutes or so, the high-pitched sound can be heard. I don't know but I think the Panic in the Woods thing may be partially proven in the video.
I don't get why someone doesn't take something like this into their own hands, it fades in so it can obviously be done with an editor, I doubt the game is also smart enough to recognise you're close to a bridge of all places, the only thing I can think that's close to that is the online vehicle spawning mechanic where you need to be close to a road.
Wasting yourself, like what happened to DaviDustin with the "Swamp creature" video can also be done with a trainer, that isn't seen or a hotkey.
Davidustin is an incredibly reliable source, however at the same time that's all the more to be abused. If he's known as the guy that debunks myths, when he finds one it can just as easily be faked. Everyone would believe him because there's no clear way of telling without going in-depth in the game files, or getting into scripting and cracking GTA V open. And not a lot of people are that smart.