I make statistical estimations in chemistry for a living, and I can tell you that the large data mining operations are sophisticated enough to do some interesting things.
But this is probably simply beyond their capabilities at this point.
Making statistical guesses as to what physiological tells there are to mass crimes could only really be predicted if a lot of people were wearing fit-bits before they decided to go on a rampage, or the tells were somehow usual.
The worrying answer would be is that it is intended as a kind of a pilot for a larger plan to eventually make something like this mandatory, or to introduce some other method of stealth monitoring through existing hardwear.