Just what was responsible for Adam Lanza's murderous assault on Sandy Hook Elementary School?
Asperger's syndrome
Guns and lax gun laws
Anti-psychotic drugs which make a condition worse
Here are three articles everyone should read:
New York Magazine: Asperger’s Is a Red Herring to Explain the Newtown Massacre (See Editor's Note at bottom of article)
Natural Society: Predictions Confirmed: MSM Says Shooter Adam Lanza Was on Violence-Linked Anti-Psychotic Fanapt
Drugs.com: Fanapt Side Effects
Of course we may never know. Asperger's advocates, gun control advocates, the gun lobby, and pharmaceutical companies all have their own interests to protect and their own means of controlling the discussion.