In response to last week's massacre in Connecticut, Mother Jones has put together a "study" on mass shootings that makes a pretty bold claim: In the wake of the slaughters this summer at a Colorado movie theater and a Sikh temple in Wisconsin, we set out to track mass shootings in the United States over the last 30 years. We identified and analyzed 62 of them, and one striking pattern in the data is this: In not a single case was the killing stopped by a civilian using a gun. There are a couple of major problems here with arguing that armed civilians don't stop mass shootings. One is that when armed civilians are present, they often stop mass shootings before they can become mass shootings. One of the criteria Mother Jones used to define mass shootings is that "the shooter took the lives of at least four people." So then, consider the following:

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