They had to have known that he was barricaded - because that's the reason they gave for their lack of action.
They could only have known that he was barricaded if he was witnessed going into the room and barricading himself.
So they had people in the school at one point.
They should have had a high degree of confidence that he was acting alone.
The RO would have a master key to everything,
Master keys are kept in the office.
Absolutely no excuse for not being able to quickly get a key.
Which means that cannot be accepted as a vali reason for waiting 40 minutes.
Maybe there are other reasons, but a locked door is certainly not one.