HELP MY CHIHUAHUA INGESTED A CANDY BAR!?

My sister's chihuahua ate half of my king size candy bar.It is 3.26 oz...and he weighs about 10 pounds.I heard on the internet that milk chocolate isnt as bad as black chocolate.He pooped earlier but it was hard and I was thinking it would be more of a diarerrah.So was this too much to where it might actually kill him? I have him dog food and a bunch of water a minute ago and he ate and drank it all up.Thanks for any information you can give me.