Here's something to consider, when they talk of mass shootings being a result of guns being "so easy to get"...
The guns (in this case "assault weapons") either in their exact present form or in a very similar form have been available on the market since the 1960s, some designs even earlier.
Guns were even EASIER TO GET BACK THEN!!!!!!!!!!!!!!
Virtually every town in the USA has a car dealer, most have several, some have dozens, but there has been no significant increase in people being deliberately run over. And there no (criminal) background check to buy a car, just the credit and insurance. You don't even need to have a valid driver's license to BUY a car. You need one to drive it home, but you don't have to have one to BUY it.
The root cause of the problem is not the guns, it is the WILLINGNESS of people to shoot other people for fun and profit. That is different today than it used to be. Why??
There are lots of possible reasons, covering all kinds of things, from education to child raising, to morals and values, religion, and many other things.
One thing that used to be accepted was that if you killed someone and got caught, you got the rope, or the chair, or the gas chamber, usually within a couple years, if not within a few months.
That doesn't seem to be much of a factor these days. The mass killers we see today do not seem to fear their own death, some seem to seek it. And, apparently they aren't bothered much by the thought of life in prison, either.
I don't know why they do it, nor, outside of idle curiosity, do I care why they do it. I have not entirely ruled out demonic possession as a possible reason, after all, I see it on TV all the time!
(sarcasm intentional)