Of course you're right that the victims here did nothing wrong, just like the Sikh victims in Milwaukee, or the victims at the Dark Knight Rises shootings. That being said, in my experience it's not really worth trying to impute a rational explanation to patently irrational behavior. Each of these people, in one way or another, just snapped, and so it's not surprising, albeit very sad, that they chose their victims at random (though in the case of the Sikh shooting it appears there was likely a clearer rationale for how they were selected, even if it was a bigoted and ignorant one).
In any case, I'm glad the bloodshed at the Empire State Building was not worse, and feel for the victims and their families.