I see no immediately possible resolution of any kind, save for perhaps at least tens of thousands of years of evolutionary process. The harsh truth is that we're currently little more than "clever animals" and the apex predators of this planet, and that we don't much "play well with others" as a staple behavior, or we'd otherwise not have made war such a popular "hobby" throughout our history.
We're always at our very best when trying to look out for each other, but that necessarily has it's functional limits.
Attacking the proper Rights of individuals isn't any magical "solution" we can even rationally attempt, lest far more evil await us afterwards. The random deaths from individual lunatics' actions, however tragic, are no reason to suspend anything approaching rational thought, and even fantasizing some "cure" for such psychotics, or any preventive measures for magically denying them weapons...well...that's purely touchy-feely fantasy for us all to indulge in over coffee, but ain't realistic in any way, shape or form. I "trust" government less distance than I can throw the proverbial elephant upwards, while I'm willing to trust those people immediately round me far more.