I hope that I would be "heroic" in that situation, but it is difficult to predict how I would act. However, given the job he signed up for, the training he had, and the equipment he was given . . . as the deputy's boss said he should have "went in, addressed the killer, killed the killer."
I agree that one element to reducing casualties is removing "gun free zones" and allow concealed carry to those who wish to (including here). Concealed carry has had positive results, it was a CDC funded study during Obama that found that guns were used defensively 500,000 to 3,000,000 per year.