Was he aggressive or just playing rough? From the description it just sounds like a dog who likes to play in a mouthy way? My friend's dog Calvin always grabs at Bianca's neck (sometimes grabs/nips and pulls pretty hard) and growls when they are playing but it is all in a playful way, and Bianca just plays back.Wondering if I am overreacting. I was at the dog park and everything was fine except there was a dog that got a little to rough with the other dogs. Well he went after my dog and he was mainly just growling and grabbing his neck.