You're right, we need at least maybe three more mass slaughters to justify doing something about it, lets drag it out until people get complacent. And only then, when everyone's tweet about thoughts and prayers become another post count increment, there will be another shooting BUT lets not be too rash. The problem is that humans are short-sighted and have short-term memory. If its not affecting us here and now, we might not feel as strongly about it until later when it happens again; just to be as surprised as the first time as to why nothings been done about it yet.
How many times have we discussed gun reform, how many people had their life snuffed short because of someone else's insanity, how many times have we lied to families that their children's, parents, and siblings didn't die for nothing, how this time it's different? How many times have we said #neverforget only to be reminded a year later from an annually timed post that today something terrible happened?
Or how about we ask a scarier question: How many more times will this happen before we decide that maybe "those" people who died may be "our" people next time? What if the next shooting isn't in the middle of a dense strip or in the packed nightclub? What if it happens in your school, or your town, or your fast food joint? Sure, it's probably not likely. That's the reasoning we use: "I live in a smaller town", "There's nothing important here for anyone to shoot", "I don't hang out with a shady crowd". If the day ever comes that you or your family and friends get gunned down because they were in the wrong place at the wrong time, ask yourself this: How many people in the US are thinking exactly what I was thinking before this happened to me.