How does Old Dan die in Where the Red Fern Grows?

Old Dan dies because of the fight with the mountain lion. Billy decides to take Old Dan and Little Ann back home, where he can doctor their wounds. While walking, Old Dan's entrails fall out and gets tangled in a bush. Billy stuffs it back in (I know... pretty gross) and carries Old Dan back home. Billy's mama tries to wash the entrails and puts it back inside, but Old Dan dies anyways. The next day, Billy buries Old Dan by a tree.