This case is so unusual. I agree with those of you in that it is much more common for women to kill their children due to various insanity reasons.
My question is, was he off medication when this happened? For severe schizophrenics, their illness does not go dormant. If they go off their medication, their symptoms will return, obviously noticeable. His wife did say he begged her to not go to work that morning since he thought the apocalypse was coming. She should have known that was a warning sign and got him immediate treatment, whether in a local hospital's psychiatric ward, or a psychiatric hospital. Maybe she was in denial of how ill he was? If he was fine for 8 years was it since he was taking his medication. If he wasn't taking any meds to control his symptoms, i'm not buying his insanity defense. With the bizarre elaborate reasons he gave as to why he killed his daughter, i would consider him severely mentally ill. It doesn't happen overnight, i'm sure someone would have noticed a change in him before that, as their seems to be a spectrum when a patient's medications get changed or they are relapsing. In most cases of mothers killing their children; the mothers being truly severely mentally ill, they can't rationalize enough to either leave the scene or dispose of the body properly. Cases range from women having a baby in an alleyway, leaving it there, to staying in the home with the dead children.
This man was able to RATIONALIZE enough not only to drive to an airport, yet to also fly out to Washington without arousing suspicions of absurd behavior that would be dominant in a schizophrenic off medication or having a relapse.
There is no doubt he has a mental disorder, yet if he was able to rationalize enough to drive to an airport, fly out of state without alerting anyone's suspicions, then did he know right from wrong?
It is such a horrible senseless crime, with no apparent motive, that since there seems to be no rhyme or reason to it, mental illness is the best answer. It is not that hard to pull the crazy card, especially with him having been hospitalized before, he would have observed other's symptoms and be able to mimick them effectively.
There are many mentally ill people out there, schizophrenics and others who are docile, on their medication and stable, able to function in society. This man's "break" seemed to occur less than overnight. Somethings fishy about this case..