A single officer might not be able to neutralize an active shooter, but he has a very high probability of at least cornering the shooter in a confined space. The deputy hiding outside had extensive knowledge of the building, a unique advantage compared to most law enforcement. The sheriff’s department response was so far out of line with current accepted doctrine that there is no question that the management needs to be removed.
What happens most often is that the perp, when he first meets armed resistance, will suicide by his own hand, rather than risk apprehension and jail. The Parkland shooter was NOT typical, possibly because he had been successful in leaving the campus and may have felt that he had "gotten away scot-free".
Well said!