In the same way that you could unknowingly boil to death if the temperature was adjusted slowly enough, it had been a gradual thing.
In later years, he would look back for a point where the moral decline had begun; to pin-point that very moment as if to be able to do such a thing would really make a difference. It took decades of soul-searching, but he finally decided that it hadn't begun with a man, but an infant.
A single child, not even a year, not even close to a year, born as what his parents were quick to insist was a monster. Blind, retarded, one arm, with one leg, no legs.... he didn't quite remember anymore. But they wanted him euthanized; an act which was as morally repugnant as it was illegal.
When doctors had refused, and when Germany had refused, the parents went over his head. They wrote to his boss, who spoke to doctors, who spoke to lawyers, who spoke to Germany. Germany refused, adamantly.
At least, at first; as he found had become the case more and more.
It wore at him, these people telling him that it was the best interest for this boy, for Germany, for the world, for the child to be out of its misery. It picked at him until his will cracked, and he allowed the procedure. And, by the time that he was injecting the child with luminal, obediently changing the medical records as he'd been ordered, he had himself convinced that they were right.
What he was doing was humanitarian, and this was an isolated case. He repeated that to himself in rapid, unceasing succession.
Even as he filed the papers away, he knew that he was lying to himself. Something in him said that he would be doing so a great deal in the coming years. But with a war to prepare for, an empire to rebuild, honor to regain, he pushed that aside and went back to work.
He hid those papers for decades in disgust; as if not revealing them was also equally moral and would make the past go away for once. It took him nearly 7 decades before he pulled them out again. Germany felt no better about it, if anything his repulsion had only grown. He wanted to burn them; as his hands burned touching them again.
But it needed to come out, and so he went through the process of publication in a businesslike manner that he'd made his own.
If nothing else, he owed it to the child he had failed so miserably to at least give him the dignity of his name back.
AN: Thank you to the commenters of the piece this was originally on; you're indeed right that it needed to exist separately. I've done so, and am very grateful for the aid in making up my mind.
EDIT: Haha, I thought this was better known. My mistake, I'll explain. 'Gerhard; is Gerhard Kretschmar, who was the first victim of Action T4. For those unknowing, this was the Nazi euthanasia program for the disabled that claimed about 200,000 lives.