@TakeV The most notable recent research debunking the bystander effect (at least in its original interpretation of "people don't take responsibility") is https://web.archive.org/web/20190510231740/https://nscr.nl/en/bystander-blijkt-wel-degelijk-in-actie-te-komen-bij-ruzie-op-straat/; likewise the wiki article on Kitty Genovese references quite a few sources disproving the original story.

I don't have references for the hypothesis that it's actually people being unsure what to do; that is an original hypothesis. I haven't seen any real research yet into alternative explanations for this sort of wait-and-see response.