Something like, it was more complicated?
If we switch to that, we can dispense with the one is "senseless" and the other is a mere "accident". I get the sense that scale doesn't matter to you. If we can prevent 100s of "senseless" deaths, 1000s of "accidental" deaths are palatable. But even worse, you're only interested in a minority subset of "senseless" murders. I think that many deaths, whether accidental or senseless are preventable, but society has decided that there is an acceptable level of risk vs tragedy on many issues. My response was to your assertion that "one is too many" which implies that they are easily preventable, when they are clearly not.
But, to me, a person shooting up a school is a complicated issue that starts with the "why" while you're focused on the "how". It is way more complicated than eliminate the currently preferred tool to accomplish the task. And as I've pointed out, even eliminated the tool is a difficult task due to technical reasons.