Making the question of gun free zones clear

VIN SUPRYNOWICZ at the Las Vegas Review-Journal makes the point very clear about the Colorado church attack that was stopped by Jeanne Assam:

Authorities and her minister say Assam saved untold lives -- lives that would have been lost, had Murray attacked in a disarmed-victim city like Los Angeles, New York or Washington.

In any of these other places there would have been no volunteers with permitted concealed handguns. In any of these places, it would have taken minutes, possibly a half hour, possibly more before someone with a gun was there to stop this attack. If so, how many people would have died? We still would be talking about this story.