[Gustoo]

Reiwa - to bolster your argument it is possible that if the cops were as cowardly as they seem to have behaved, its possible they would have been less afraid of the shooter if they somehow knew for a fact that the shooter had less effective weapons than they did so the shooter would have had less than a full hour to take 15 lives.

Unsunghero - I agree. The liability on a cop running into a school guns blazing potentially accidentally shooting a kid or something makes them much more risk averse in these situations. When they can cede their responsibility to the "proper authority" in this case a SWAT officer, they seem more likely to do so.