Well here we go again.

[denton]

Why do you suppose these incidents happen at schools, churches, and hospitals, rather than shooting ranges, gun stores, and police offices?

You don't need a large percentage of the population to be armed. If, on average, 1% of the people are carrying, the probability of having at least 1 firearm in a group of 100 people is 73%. If 2% carry, then the probability is 87%.