For the purposes of their study, they identified mass shootings as incidents in which four or more people were killed. Right of the bat, this suggests their conclusion is somewhat fallacious. The whole point is that the presence of other armed people on the scene might stop mass shootings from becoming mass shootings. Anyway, I cited a random sampling of examples where exactly that happened. A number of those incidents involved off-duty cops and I acknowledged this explicitly, while making the distinction that Mother Jones’s definition of “civilian” seems odd and slippery…