meanwhile , un-discerned and indiscoverable to them , busiku , having took out a short serrated knife from where it was strapped on his waist just next to his belt , chopped off thin but long branches from a nearby giant tree and began carving their brims until they were sharp , and then , cautiously but secretively , he went after the scattered canis one after the other , sniffing and butchering each one of them until they were all dead .