Well this kind of thing isent THAT rare..(kid muder/murder attempt on his own parents)especialy not in anime xD.
It happened here in Romania to...girl killed her own Mom with a damn surgery knife 43 stabs i think(Killers these days are so stupid...why 43 if one in the heart is more than enough >_>)She turned out to be twisted therefore considered unguilty and actualy thought to be suciety suited after 3 months of therapy and after that she even sued the mass-media for 300000$ for giving her picture and full name the day after the murder.(Talk about the nonexistence of karms >x>)
But to be most honest...i would rather feel sorry for the parents on who thekids failed to kill in the atempt...cause regardless of what they do they will forever have to live with the fact that the thing they themselfs gave birth to and raised prob hates them and wanted/wants to kill them...as much the parent cares/cared about the kid as worse the parents mental health will end up after such a thing.