Yes, the increasing frequency of these homegrown attacks and school shootings should raise questions about our culture.
And explanation is not the same as moral justification.
I think compulsory public schools and undergraduate classroom-based colleges are very repressive against individuals, without fluid and free avenues for grievances to be aired and needs to be met. Sit up and shut up. The answer has been to use psychiatric drugs, punitive incarceration and behavior modification against individuals, rather than addressing broader social issues.
Partisan bickering between politicians about short-term reactionary policies sidetracks us. Gun control, enhanced interrogation, etc. -- those are not addressing the real underlying issues, and are just kicking the can further down the road until there's another attack.
I do not find it a coincidence that most of these young people accused of mass shootings or acts of terrorism, are current or recent members of our school system. I would absolutely explode and probably go to prison if I had to deal with today's zero-tolerance school systems.
There is something about mass public education which diminishes the individual, and makes small local corrections impossible because there are no outlets for grievance or ways to meet existential needs. As a result, anger, anxiety and depression build up in a person until s/he has no other outlet than to hurt others, no matter what the personal costs.
I find it very sad that media focus on whether suspects are members of certain "groups", or whether suspects have been labeled with pseudoscientific psychiatric labels, or whether their parents were "good" or "fit", when really, it's a much larger social context, and public institutions, which lead to the behavior.
A good book on this topic: http://www.amazon.com/dp/1595230769
The War on Kids: http://www.thewaronkids.com/