It should have been killed, however Candy should have had some courage and done it himself.
He was suffering. It was humane, but as he say, Candy should have done it himself.
The dog was old and could barely move. If I was in the same condition as the dog, I'd want someone to end my life so I wouldn't have to suffer.
NO, he should have been able to die when he died, it was a power trip over Candy to show him he was of no use.