The detail about the door answers one question. Locked doors are good, but, ballistic breach is always a possibility. Especially for glass doors. Doors buy time for violent solutions to be mustered, that's all, they're not a solution themselves.This is the most detailed article I've seen so far
Nashville school shooter was transgender, had ‘manifesto,’ police say
A heavily armed woman killed three 9-year-olds and three adult staffers Monday at a private Christian school in Nashville before police shot her dead, in a rare mass shooting carried out by a female suspect. Police said shooter Audrey E. Hale, 28, a transgender person who identified as a male...m.washingtontimes.com
From the sound of the equipment and planning, the school got off light. Sounds like some victims were immediately upon entry and others on the second floor, followed by getting shot by the police. Perhaps classes were in session and locked, limiting the availability of other victims. Or maybe there was some specific target on the second floor she was more interested in.
The worst school shootings have happened when a killer gains access to a classroom full of contained targets. Massive lucky break to have avoided that here. Nashville PD immediately closing with and eliminating her probably made that difference. It's just too bad the school doesn't seem, at this time, to have had anyone in place to engage the shooter themselves. 14 minutes is a long time.
Waiting to see if the manifesto bears out whether the story here is a hormone raging troon deciding to put "kill terfs" into praxis.