[muawiyah]

The staff at this school didn't let him through ~ he shot out a window and let himself in, and started killing.

The only armed guard arrangement that would work is to station an armed man in bullet proof cupola ABOVE the main ~ and ONLY entrance ~ just like liquor stores do it.

[AbnSarge]

My 11-year old daughter figured this out:
Dad: “What’s the only thing that can stop a bad person with a gun?”

Daughter: “A good person with a gun?”

She then named three people in the staff at her school she thought would be pretty trustworthy (and ballsy enough) to take violent action to protect the kids there.

Read where the custodian ran up the hallway yelling a warning. How about if he was reacting with his own firearm?

You can’t stop all of the attacks, but you sure can limit the casualties.