Some people are actually unfixable and destined to commit horrific acts of violence, this we know unequivocally. The only way we can prevent it is by screening

Some people are actually unfixable and destined to commit horrific acts of violence, this we know unequivocally. The only way we can prevent it is by screening and monitoring people before it happens, and we've got a pretty good idea of the precursors for this kind of thing. I doubt society would consent to such interference in order to prevent a few deaths from these rare individuals. Additionally for true prevention we would need to stop certain people from having and raising kids, now... that's a can of worms I am not sure will ever be opened.