Pitbull Rottweiler almost fight

Well not really between 3 good owners we had all angles covered. SO we were waling in the park and just about 15 minutes earlier chaos (pitbull) was bitten by a german shepard. NOTE THE PITBULL DID NOT START THE ATTACK NOR DID HE RESPOND AT ALL EXCEPT TO WALK CALMLY BACK TO HIS OWNER AND SIT. So we come up to this rotti with the 5 month dogo 3 year old child and 2 pugs off leash. Chaos is on leash and is the only dog kinda kept from smelling. Anyway eventually Chaos attempts to mount the rotti and gets corrected by ius attentive owner and the rotti. Nothing vicious just how dogs communicate but could have gotten bad because although well trained this pitbull is rather dominant and also should be bred soon as he is not fixed.