Lucky the tree didn't fall on him, and a miracle his chainsaw didn't get stuck. He doesn't know how to correctly cut a tree, that was terrible technique!
It was a hollow trunk and he didn't want to chop his dogs legs off. That's why he only cut through the trunk from the side with less branches so that when he got to the heaviest part it pulled the tree over that way. EDIT..... have to say it was well filmed but the dog should have been jumping out of the stump not running out of the trunk (unless it was a really good climber to scale the inside and get out of the way )
When I was watching it, I was thinking he's cutting that tree all wrong, then the dog appeared and I'm like, ah I see.