A lot of people probably like to think that they'd be a hero in a threatening situation, but from what I've observed with humans, is that most of us are more interested in preserving our own lives at the expense of maybe sacrificing ourselves to save someone else. It makes sense- in the face of unspeakably evil acts, like the knife attacks which started this conversation, I think most people would not know how to react, whether or not they have a weapon of some kind. And even then, in those moments where the fight or flight response kicks in, the majority of humans would be overcome by their instinct for self preservation, and not equipped to handle their weapon effectively
