I imagine most of us only kill when we find it necessary.

[ (Don't worry, it's just a joke - it's why Alice says it so dryly.

Because it's easier to think about this and talk about it like this than truly contemplate the dangers of having some people on this very cramped train.) ]

But if he did kill someone back then, we would certainly have heard about it. It is not as if such a thing can happen secretly in a place like this.