Evidence? What evidence is there that some locations weren't chosen because they were gun-free zones? What evidence is there that the killer was not familiar with the lack of guns on a location, such as where he worked, even if it wasn't designated a gun free zone? If the majority of FBI defined mass killings were domestic in nature, occurring in private homes, which were obviously not designated as gun free zones, what evidence is there that the killer was not familiar with the lack of guns or where they were in those homes, especially if the available gun was in their hands?
A couple of the articles or "studies" that I've seen, which claimed to destroy the so-called "myth" of gun free zones, try to emphasize the personal motivation of the killer over the choice of location, and then insinuate that, therefore, the reason for the shooting was not the gun free zone. That is a straw man argument, since it is mostly not claimed that gun free zones are motivations to kill, but that they make it easier.
And then those "studies" bring up statistics such as 67% of mass shootings happened in private homes and only 15% in public gun free zones, and 30% in work places. Well, that 15% (another anti-gun "study" claimed that there were "no more" than 25%) occurring in gun free zones is "evidence" that, for some (15 to 25 percent), they are attractive locations.
So, even though private homes are not classified as gun free zones, as I said above, the shooter's knowledge and familiarity with who has guns and where they are, and the advantage of having the gun, perhaps the only one in the home, in his hand while his victims are unprepared for what is about to happen, gives the shooter a "gun free" advantage when he faces those unarmed victims he is about to shoot. A similar knowledge and comfort level exists in a workplace mass shooting.
So, granted that the motivation for the domestic or workplace shootings, as well even in the gun free zone ones, is not the location, the shooter is well acquainted enough with those locations to know he can either kill all of those he is really "motivated" to kill, or a good number before he is stopped. If he is stopped. And this is true, using the above statistics, in the vast majority of mass shootings.
On the other hand, if the killer actually knew that each person in the location of his choice was well armed and trained, would he be as likely to choose that location? Do we have "evidence" that no mass shooter would choose a place with less resistance?
I did a quick check on the subject and these are the first four I saw:
http://www.breitbart.com/big-governm...un-free-zones/
http://www.nationalreview.com/articl...john-r-lott-jr
http://www.usatoday.com/story/opinio...ntrol/1770345/
http://www.american-partisan.com/cols/brown/080800.htm
I found a few which disputed the gun free zone "myth," but they had the typical straw man arguments. I suppose, if your inclination or preference is to believe them, then for you there is no "evidence" for the gun free zone "myth." I got a kick out of one anti-myth study which said:
"To put the improbability of mass deaths occurring at school in context, consider that the total number of handgun deaths in the United States (1980-2006) was about 32,000 per year. By comparison, since 1980, 297 people have been killed in school shootings. This amounts to roughly 9 deaths per year at school. Essentially, John Lott and other gun-advocates want teachers, professors, and security officers carrying guns in order to deter extremely unlikely events, a policy that has no substantiating evidence."
So all this urgent fuss about needing more gun control laws to make our schools safer from mass shootings is about deterring "extremely unlikely events."