The bugaboo about people "snapping" is largely myth, anyway. These mass murderers who've been all over the news the last very few years didn't "snap;" they've been proven to have meticulously mapped out and planned their attacks long in advance.
And I think it's important to note that they deliberately choose peaceful, idyllic, "safe" settings to carry out their attacks. Schools, theaters, shopping malls, Amish schoolhouses, Norwegian youth summer camps.... Mainly because there's very little chance they'll run into anybody around who can return fire, but also because these contain the most symbolic value....i.e., you're not safe anywhere. So, perversely enough, the safest places are the places you're most likely to run into a mass muirderer.