Typically I'd agree with you, but this statement here...
"Tatro said she was 'looking forward to Monday's embalming therapy"
Is reason enough to be concerned. When some kind of school shooting happens, there is typically a message before hand. Sure, you can shrug off the "I wana cuta bitch" but when you make statements like the one posted above, there needs to be some kind of action.
Let's take for granted that "When some kind of school shooting happens, there is typically a message before hand". That does not, in any way, imply that every time you encounter such a "message", there's a statistically significant chance that a violent act will follow.
In fact, most people will agree that most "threats" of this nature do *not* result in violent acts. There thousands, if not millions of "threats" like these, uttered idly every day -- a simple hyperbolic expression of frustration. Meanwhile, school shootings happen a handful of times a year, at worst.
Similarly, I can guarantee that almost every school shooter will have imbibed some form of liquid before committing their heinous crimes. It does not follow that everyone who has a drink with their breakfast is going to shoot up their school.
"A usually precedes B" does not necessarily mean "A has occurred, therefor B MUST occur."
It doesn't even necessarily mean "A has occurred, therefor B is even 1% likely to occur".