I don't know what to make of this. Our now almost 7 month old black lab puppy has been around a lot of other dogs, he has always been playful and never has shown any kind of aggression in any way. We also have n 11 year old black lab who is never aggressive to the puppy. Yesterday some one we kind of know stoped by on his walk with his 4 1/2 month old black lab puppy. He has stopped by before and our puppies have interacted maybe 2 or 3 times. Yesterday he stopped by and we were out back with the puppies and they were running around chasing each other, sniffing each other ect. Our puppy is very much into playing ball so we got out his ball to throw it since the puppy was playing with our other dog at this time. We started throwing the ball and his puppy would run along side our puppy and not try to take the ball but just run close and he would put his head by our puppies head. Just playful not trying to take the ball, not trying to knock him over or anything. Well after a bit, the puppies were standing there and our puppy had his ball he turned and growled what sounded aggressively and showed his teeth to the other puppy, the other puppy just walked a few steps away and layed down Then got up shortly after and started runnng with our puppy again and nothing everything seemed fine. We stopped throwing the ball and he was dropping his ball near the other puppy and me but this worries me, should I be concerned?