Duke was a BIG guy and armed.
The school board was unarmed and a bunch of people used to resolving issues by sitting behind desks and palavering - their SA was wholly lacking for such a situation as this one and their only recourse (as they saw it) was to apply what they knew...which they did.
Duke was crazy and looking to become a martyr.
The situation may have turned bloody if Duke had been rushed - he wasn't, and the only person shot was Duke himself...a fairytale ending.
I'd wager they'll have a better security presence at any such meetings in the future.
Coulda-shoulda-woulda...and so it goes...
Richard