'Insanity! It seems to me that he would have been insane if he had NOT killed them.' Surely it was wiser and better and kinder to send them all to sleep, than to let them continue to suffer.
At the same time he thought it very strange that the man should have chosen to do it that way, when there were so many other cleaner, easier and more painless ways of accomplishing the same object.

He wondered why it was that most of these killings were done in more or less the same crude, cruel messy way.

No; HE would set about it in a different fashion.

He would get some charcoal, then he would paste strips of paper over the joinings of the door and windows of the room and close the register of the grate.

Then he would kindle the charcoal on a tray or something in the middle of the room, and then they would all three just lie down together and sleep; and that would be the end of everything.