awwwwwwwwwwww thats soooooooooooooooooooooo sad...
Im sorry I dont know why he would do that... but I was thinking about what you said about building up his confidence... and I was thinking have you tried agility? I heard it does wonders on their confidence levels!!! Ive been looking into it and where I live I have yet to find a dog agility classes...
just a thought
good luck and I hope you can figure out why!