I think it's more than just access to firepower. Other countries have access to the same firepower, yet we have far more things like this happening. I hate to say it, but we are just broken and I don't know that there's a way to fix it. There are people in our society that have no regard for human life. It's sad, it sucks, and I do hope that there is something that can be done. I don't want the solution to be more security in our schools, having more people armed, or any other ideas like that. I'm a supporter of the 2nd amendment, but there has got to be something better than more people armed. I have weapons, but they do not leave my house except to shoot at a range. My weapons are for peace of mind within my home. If someone were on my property and stealing something outside, they can have it. I'm not going to kill another human being over a "thing". Maybe I'm in the minority of other gun owners, but for anyone to be on the wrong side of my weapon, they will need to be in my house and a threat to my family.
When I was a kid, my dad taught me how to shoot when I was around 11 or 12 years old. The very first thing that he told me was to never point a gun at any other person or animal unless I intended to kill. He taught me that every gun was loaded, whether you think it is or not. My dad and I both served in the Marine Corps, so we had a bit more training than the normal person on the street.
I guess the bottom line is that in my mind, we're simply screwed up as a society.