In order to function as intended, the confiscation or restriction of arms depends chiefly upon the cooperation of the vilest elements of society. As Cesare Beccaria wrote referring to the absence of the right to bear arms: “it disarm only those who are not inclined or determined to commit crimes. And all the while, those who have the courage to violate the most sacred laws and the most important codes, how will they respect even the minor or purely arbitrary laws?”
They won't. Criminals everywhere have guns, and they always will. Gun control simply takes guns away from those who would normally abide by the law, in turn rendering them more vulnerable to attack. As c13 stated, most, (actually, if I'm not entirely mistaken--all) mass shootings to happen in the United States, and even in Canada took place within gun-free zones (concealed/unconcealed carry is not permitted in Canada and self-defense there is not considered a legitimate use for a firearm). After all, the last thing a bad guy with a gun wants to see is a good guy with a gun--whether it be a police officer or a law-abiding gun owner.
On a philosophical basis, the right to bear arms is undeniably just. That is, if the foundation of your worldview is liberty. The two most important tenets of Western civilization are life and property. From these flows liberty. It is my opinion that a government has no moral basis for denying its citizens a right to defend themselves, their family, and their property. If you cannot be provided the means to adequately and legally defend yourself, you cannot claim to reside in a free society. Indeed, a free man and one debarred of arms are mutually exclusive propositions.