I agree with your last sentence. 
If there is indeed a problem with the culture, wouldn't it be a good idea not to exacerbate the problem with easy access to firearms? 

Mental illness is not uniquely American among advanced industrialized countries. Yet most advanced industrialized countries have nowhere near the level of homicides by firearms that we do. Then again most advanced industrialized countries have some form of universal health care that includes treatment for mental illness as well as far greater restrictions on firearm possession. 

If we couldn't get firearm restrictions after Sandy Hook, we will not get them at all. So the only other option is Universal heath care that includes treatment for mental illness.