The world, on the whole, is a safer place than out was decades ago. More coverage of violence does not equate to more violence. Complaints about losing moral compasses are emotional arguments, not empirical ones. Which of course in no way excuses killings like these.
I usually err on the side of personal freedom, and that's my default thought on gun control. But then you have data points like what Australia did that seem to support much more gun control. I won't pretend that there aren't good arguments on either side, but I'd be curious about what data we have that doesn't serve some agenda or other, which is hard to find.
Also, depending on the source, atheists make up about 1-4% of the total US population (the umbrella term "nones" includes MUCH more than atheism). Gun supporters occasionally make some cogent arguments, but will have to look elsewhere for their cultural scapegoat here.