"This is why their should be a licensing test to own a weapon"
I don't disagree. Most states have hunter education requirements to obtain a hunting license, those courses with which I'm familiar include significant firearm handling instruction.
However much training is required, however, remember there is also a licensing test to drive a car. To paraphrase the late, great George Carlin, think about how stupid the average driver is. And remember that's the average, half are dumber than that.
Also, widely attributed to H.L. Mencken, "no one ever went broke underestimating the intelligence of the American people."