AURORA, Colo. (AP) — It was deafening when a dozen teachers, parents and school staffers from across Colorado stepped up to the yellow line of a gun range and fired five rounds from their handguns, in tandem.

Empty shells bounced like hail across the tight line of shooters. The shells already covered the ground from the day's exercises of training about two dozen volunteers to stop a school shooter.

The shots were on-target. If the teachers weren't already authorized by their school districts to carry a handgun in their school, they likely would be after passing the final shooting test.

Shoote...