Man punched kangaroo after it attacked his dog

A video has gone viral of a man punching a kangaroo after it attacked his dog.

From watching the video it seems the kangaroo and the dog had an altercation, and the kangaroo manages to get hold of the dog in a headlock.

The man then runs to his dog's rescue, and as he approached the pair, the kangaroo lets go of the dog and stands on two feet ready to take on the man.

The man then throws a punch at its face and connects.

The thing is - if you watch the video, you'll see the kangaroo actually let go of the dog, so why doesn't the man just leave it there?

Why does he still have to do round one of a title fight with the kangaroo?