First, we take chances everyday from the moment we get out of bed. Life is too short to be worrying about every potential hazard. You could die in a car accident on your way to work. People still drive. You would be surprised how many are discovered dead on their pot. People still shite. You could walk out in your yard, slip, fall, break your neck and die. People still walk in their yards. I could continue on this one but I think the reader should have the point by now.
Second, there have always been kooks and there always will be. Nothing you can do about it.
Thirdly, literature has been rife with violence over the centuries. Look at how brutally Caesar was murdered. Sheakspeare was not banned.
Last, controlling guns is not going to be the answer. If the guy did not have a gun, he could have fixed up a bomb and thrown it. Same difference.
No one should be taking the brunt of anything except the criminal who did the deed, and in his case - justice should definitely be done.