That is a very valid point and brings to mind another, if not directly related, at least adjacent point: what the definition of a mass shooting is and how it's defined. If you said "mass shooting" to the average person what would spring immediately to mind is something along the lines of Uvalde, Parkland, Las Vegas, Sandy Hook, or Columbine: a crazed gunman indiscriminately shooting large numbers of innocent people. However, by definition, a mass shooting is any incident in which four or more people are shot. The vast majority of mass shootings, which are included in the often bandied about statistics of "x number of mass shootings in y period of time" are shootings of relatively small groups of people by someone they were related to, closely acquainted with, or had dealings with. A gang-related shooting in which half a dozen drug traffickers are shot is technically a mass shooting, but that's not the perception that most people have. By definition, mass shootings are not all that uncommon in inner cities and other high-crime areas, but they don't have the media "shock value" for Suzie Q Soccer-Mom because, unless you're related, acquainted, or have dealings with violent criminals, you're at relatively low risk of being a victim of this sort of mass shooting. While the loss of life from these more common shootings is certainly a serious problem, it doesn't resonate like the "crazed gunman" type because it doesn't directly affect the life of the average middle-class suburban voter (or at least they don't perceive it to).
Again, we have the issue of inconsistency on the part of how "disturbing behavior" by juveniles is handled. On the one hand, you have a reluctance to do anything because "he's only 14" and "I don't want to screw up his life" but on the other hand we've all heard stories of gross over-reactions to relatively minor things due to "zero-tolerance" policies. It is at the very least eyebrow raising that a 14-year-old making threats of violence is swept under the rug when we live in a day and age where kindergarteners have the police called on them for pointing a finder and saying "bang, bang" or chewing a pop-tart into the vague shape of a pistol. Perhaps, rather than clutching pearls over a five-year-old's breakfast, we should focus on actual threats of violence by teenagers. There are, after all, options somewhere between ignoring disturbing behavior and ruining a juvenile's life. Perhaps, if the threats of the 14 year old had been taken seriously and he'd received some mental health treatment at 14, he might have been able to work through whatever mental/emotional issues he had and wouldn't have wanted to shoot up an Elementary school when he was 18. Mental health, however, is a far more complex and nuanced issue than gun control and it doesn't fit on bumper stickers, increase television ratings, or drive a political agenda nearly as well.
I agree and I think a lot of this has to do with a very black-and-white mentality about mental health. On the one hand, you have the old way of thinking in which anyone with a mental illness should be locked away and institutionalized. This school of thought stigmatizes mental health care and discourages people from seeking the help that they need. On the other hand, you have a school of thought that is so concerned about stigmatizing mental health issues that they are reluctant to even acknowledge a problem when it exists. This is equally as dangerous because it quickly devolves into denial that there is even a problem, dangerous or not, in the first place. Yes, the majority of people with mental/emotional health issues are pretty much harmless, but even harmless mental illnesses can fester into dangerous ones if left untreated. If we want to get to the root of mass shootings, perhaps acknowledging and addressing the fact that mental/emotional disorders of all types, including suicide and self-harm are increasing. The issue, as I see it, isn't "mass shootings" or "gun violence" but rather mass murder and violence of any sort. I think it would be much more productive to examine why an 18-year-old wants to kill a bunch of small children than wringing our hands about the manner in which he chose to do it.
) is "mental illness". 
