I think your reasoning in this post is pretty inconsistent, since I'd say "adding [guns], or rather a [particular sort of] gun-oriented [...] culture" is the main reason we have mass shooting deaths, too.

Sure, guns are not sufficient to produce mass killings without the context of a certain attitude towards homicide. (Justifiable homicide in particular, but that isn't complete without the question of "justifiable to who?" and its relation to attitudes about homicide in general.) But that division in attitudes is the crux of the conflict!