In a parallel universe, those events might occur, but in THIS universe where we’ve had widespread CC for years, they haven’t.
I agree. That’s because those who go to the time and trouble to obtain a CCW permit are, more or less by definition, responsible people.
But they’re also probably considerably less than 1% of the population at any given time.
The article is about the (reasonably obvious) fact that if an armed responsible person is present when a mass shooting starts, it’s a lot more likely to get stopped before many people are killed.
But the chances of such a person being present at the right time and place are poor, because so few people go armed.
To stop most or all such shootings in this way, a great many more people would have to be armed. Which would create unintended consequences, because that much larger number would include people who aren’t responsible. Many people aren’t.