Unnervingly, to our knowledge Adam Lanza never gave any outward expression to the malice festering in his head. Before that awful Friday, he wouldn't have appeared necessarily more dangerous than any other shy, quiet young man.
Around 270 million weapons in the US are kept legally in private hands. Presumably, a good proportion of American gun owners have families – including college-age boys still living at home. Every such American is thus guilty of the exact same dereliction as Nancy Lanza was. Do they all deserve to die? Indeed, any gun owner assumes the risk that the weapon will be misused, perhaps to horrific effect.