In modern society, it's not a positive thing for a country to have even a sole mass shooting connected to its history.
However, in a society where most firearms are not illegal but are strictly regulated, having one mass shooting every decade does provide substantial evidence that it does work.
Unfortunately, America is a different animal and there is no "one-size fits all" solution for its long ongoing mass shooting problem. What works for the UK or Australia for instance doesn't equate to what would be effective in America.
I do not claim to have the antidote for such an issue as complex as this, but certainly, something needs to be done.
That begins with both sides of the argument to stop insisting that their way is the only way, and find some middle ground to build a foundation on for the best interest of the American people.