That would depend on what your definition of "conventionally disturbed" is. Most modern diagnostic psychology is based upon deviations from some kind of norm (it's greatest weakness, because then you have to define the "norm", not easy to do objectively)

..but it doesn't change the fact that most people would find the idea of picking up a weapon and killing random innocent people to be completely abhorrent. Given that definition, yes, I could see how "disturbed" or "mentally ill" fits. Having the mindset that committing mass murder is okay or justifiable is an aberrant thought pattern. Full stop, end of story.

Address that pattern, and you address the root of the problem.

I find the idea that "desensitiation to violence" is at all meaningful to be spurious at best. More tractable types believe the media narrative about, say, Columbine being caused by the shooters being avid fans of the FPS game Doom, but study after study can't find a link between games and real life violence.

There's also proof by inversion - the USA is famously inverse of the rest of the world, puritanical when it comes to sex, okay with violence. Therefore, you'd expect if the desensitization idea held any water, that the rest of the civilized world has a bigger problem than the USA with sexually-based crimes. I haven't seen evidence to that effect.

  > most people would find the idea of picking up a weapon and killing random innocent people to be completely abhorrent. 

Killing random guilty people, on the other hand, is completely legitimised in the USA. Self-defence advocates talk about it all the time. So all that has to happen is for someone to manufacture a justification for the victim(s) deserving it and it becomes legitimate in their eyes.

That's how lynching used to happen; entire communities would turn out to murder some people simply because they were black.

I wasn't talking about games being the desensitising factor. I'm an avid player of games myself, many of them very violent. More about a climate where mass killing is more visible and has less repercussions or damnation - e.g. war.

US has been in more wars as the aggressor than any other country I'd guess, over the past couple of generations. Perhaps that mass death and resulting inpunity for people at the top contributes to these teenagers' lack of appreciation of the horror in their actions?

I agree 'conventionally disturbed' is a silly term. Hard to find one better; maybe, 'absent of any identifiable mental disorder that would likely explain their murderous actions'?

you've got the wrong idea about drone pilots. people who do it do NOT see it as a video game. they follow orders, some they'd rather not, but if not for duty.