In case you missed it in the overview, the exact quote is repeated as the very first line of the "Characterizing the Attacker Section" on p. 19. And just to be absolutely sure, the explanation then begins by restating it this way: "Although all of the attackers in this study were boys, there is no set of traits that described all or even most of the attackers."
Wyatt's next point was that "most school attacks, the report said, come from loners with some kind of grievance." His point was repeated on-screen with a graphic that said "Most attacks: loners with grievance." Actually, the said that most are not loners.
No, seriously. I don't know what report Wyatt was reading, but the one he cited has a little section on the attackers social relationships on p. 20, where it says "The largest group of attackers for whom this information was available appeared to socialize with mainstream students or were considered mainstream students themselves (41 percent, n=17).
Later in that section it specifically addresses loners: "One-third of attackers had been characterized by others as 'loners,' or felt themselves to be loners (34 percent, n=14). One-third--meaning two-thirds did not. So most school shooters are not loners, outnumbering those who are two-to-one--yet Wyatt insists the report made the opposite conclusion.
I stared at the screen speechless. How he could so dramatically misrepresent the main findings of the report was beyond me.
He was correct on the point that the study found 71 percent of the attackers felt persecuted, bullied, threatened, attacked or injured by others prior to the incident.
The loner myth has been going on all day. CNN was talking about it all morning--how these shooters all turn out to be outcasts and loners. No, what actually happens is that the media got the loner/outcast narrative down years ago, and always jumps to that conclusion, so the repetition convinces them that it's true. In the Virginia case it's looking like it was true--however, in Columbine, and two-thirds of the other cases, it was a wild misconception.
The larger point is that the media does the public a major disservice by trying to convince us that there is such a thing a particular profile that these shooters fit. They try to fit all these ghastly events into a single personality type that we can be afraid of, but it's just not so.
The other major study of school shooters was conducted by the FBI, and it came to exactly the same conclusion--and warned of the dangers of this behavior by the press. One of the first major points in its introduction was:
"One response to the pressure for action may be an effort to identify the next shooter by developing a `profile' of the typical school shooter. This may sound like a reasonable preventive measure, but in practice, trying to draw up a catalogue or `checklist' of warning signs to detect a potential school can be shortsighted, even dangerous" (p. 2).
So really, stop already.
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The study cited by CBS above is online here (It was actually a joint study by the Secret Service and Department of Education. It studied all 37 cases of school shooters between 1974 and 2000, using a very reasonable definition of school shooter.)
The FBI report is here