Why did Ruben fall on the ax in Where the Red Fern Grows?

Because he was running with an ax to try and kill Billy's dogs since they were killing his dog but he triped on a stick and accidently stabbed himself. That is true, but, he was running to get to Billy's dog, Old Dan, to kill him and fell on an axe that went right through his stomach. He made Billy pull the axe out of him (eww!) and died right after that. This is a very good book, right up til the end. I was bawling by Chapter 20!