[grobdriver]

It is known that Hale considered the actions of other mass murderers

Rule one for mass murderers: Select a gun free zone.

[CatHerd]

At least one school staff was reportedly armed:

https://nypost.com/2023/03/31/nashville-school-staff-were-packing-guns-911-caller-said/

Of course the mass murderer may well not have known that.