I've just got back from a ruined walk with my 8mo collie puppy. We had been out about an hour and he had been playing with my parents border terrier with a football in the snow on the field next to my house.
Little terrier got bored so we went our separate ways. As I was walking along I carried on kicking his ball until we got near to where some children/teens were sledging down a bank next to the exit of the field.
I called pup back and he came straight away, as he always does and sat infront of me waiting for his treat and to be put on his lead. Then out of the corner of my eye I saw a massive lurcher/shepard x hurtling towards us out of nowhere. At first I thought it wanted to play, but as it got to us it started barking really aggressively and smacked right into the side of pup and knocked him flying 
Pup bolted with his arse touching the floor terrified with this dog still barking and growling and snapping at him. While all this was going on some little sod that was sledging was screaming "get him! Fight fight fight!" Cue hysterics from the other brats he was with. The dog eventually went back to them and I managed to round up my poor collie.
As I got him on his lead the bloody thing ran straight back and grabbed him growling! I had lost it by this point and screamed to get it on a fucking lead 
I was then met with fuck offs and we don't want to. I was shaking and so shook up. I managed to get away and my poor dog was shaking like a leaf.
I'm sorry for the epic post but I am just so upset. Is this going to ruin my dog? He's great with other dogs and I'd hate for it to destroy him
When we were walking away my pup started properly barking at the dog and he's never done that before.
I'm all over the place.