Prior to 1968, anyone 5 years of age or older in the USA could buy a gun and ammunition, yet there were NO mass shootings. None. Ever.
What has changed since the middle of the 1900's? We've spent decades overtly and covertly destroying all of the things that encourage and support strong families, and taught children that life is period of meaningless pain and suffering wedged between two periods of non-existence, and we wonder why these things happen?