Most of the rhetoric about gun control is off target assuming one is "shooting" at effective prevention. One needs to "follow the money" since "the business of America is business".
Even in the USA there are those perfectly willing to impose disadvantage so great upon others for personal gain as to qualify as potential tyrants. Private gun ownership is one of many conditions together capable of giving their suppressible sociopathic tendencies pause.
It's not hard to see that we presently have the well sprouted seeds of economic tyranny. The economic gap between the wealthy and the masses here in the USA hasn't been this great since before the great depression of the 1930s. We've gone from ~50/1 ratio, top corporate executive compensation to average worker pay in ~1970 or 1980 to the present ~500/1 and possession of share of the nation's personal wealth has followed that trend.
The economic stress sustenance of that great an advantage for any minority imposes on any society in times of a shrunken economy such as today results in abandonment of efforts to support those of less psychological resilience, like this shooter. Some will "go off" as a result. Some will do so in this manner. It's actually a wonder we see so few of these events. Again, as a society whose economy is about profit and who gets what share of it, follow the money. That's where the source and solution lie.