Might be an unpopular opinion but I don't actually hold this against these people too much because I think most people would be similarly stunned in this situation and have no idea how to react other than to gawk and not draw attention to themselves in the wake of a knife wielding psychopath. What do you even do to treat a knife wound to the throat that probably hit an artery? Apply pressure?

We live in a low trust society, none of these reactions surprise me in the slightest.