I guess kid was a hero for saving the dog. Think a man with a sword plus a pit bull would usually atleast scare away a mountain lion. However, he was taking a big chance to return to the seen and confront the lion at a close distance. Doesn’t seem like a great idea.
In this article, he also describes the cougar as the same size as his dog. In the other story, he said it was twice as big. I think it was probably a young, small cougar, otherwise it would have eaten the dog long before the kid got back.