Spoilers ahead
Histeria was more likely triggered by Chase and TJ who came to Echo, the fact that they conceal murder was enough to start everything again:
"You are only moving in circles" - (TJ route again, it is the most important route in my opinion)
Chase misinterpreted Sydney when he was "drowning" Toby (Toby changed name after that and is known as TJ), bc of this otter drowned him and have sworn that they will hide the truth -> after that everyone's problems got bigger, especially Chase's (night terrors, sleep paralysis, hallucinations) -> gang is leaving Echo -> a few years later when everyone came back histeria should get started, however in this only route it didn't! Because the game that Syd made up was supposed to reveal otter secret and bc of that histeria wasn't necessary -> Alas, in the last moment Chase got possessed again and when the truth was finally revealed to Flynn, otter *sob* killed gila to hide his sin. Chase made full circle, now he will leave Echo and hide to the end of his life the next mystery ;-;
Don't think about being "distorted", it is ghost after all :)
I had no idea who this "Gila" was, so I wrote it in goggle and found that gila is the reptile species = Flynn species, its the same when we call Chase "The otter" or TJ "the lynx"