In footnote 40 of his article The Impact of Concealed-Carry Laws (in Evaluating Gun Policy), John Donohue comments on Lott’s claims about multiple-victim public shootings:

In the wake of a recent school shooting in Germany that killed 14, Lott summarized his finding from the Lott and Landes study: “multiple-victim public shootings fell on average by 78 percent in states that passed [right-to-carry] laws.” John Lott, “Gun Control Misfires in Europe,” Wall Street Journal, April 30, 2002, A16. Although the results may at first seem persuasive, there is a major problem with the Lott and Landes data. The FBI Supplemental Homicide Report (SHR) reveals over 800 such multiple-victim deaths per year while Lott and Landes use a Lexis search that generates only about 20. While it may be that not all 800 should be included (e.g., Lott and Landes would eliminate some of the murders in the FBI data because they are not committed in public places), the true number of cases is vastly greater than the number that Lott and Landes employ. Indeed, Lott and Landes have now found that when they use the SHR data, their results “were rarely statistically significant.” Consequently, if their story doesn’t emerge when they use the best data, why should we believe their results using much less accurate data?

Whenever a major public shooting occurs, Lott writes an op-ed claiming that concealed-carry laws would largely eliminate them. He never mentions the problems with his data or the contrary research. No doubt he is working on one now in response to the Lockheed shootings. This one occurred in a concealed-carry state, but I imagine he’ll be able to come up with something.