I dunno LB, not sure about this one. I'm assuming we are talking about an offleash park but I could be wrong.
It's normal for an older dog to tell a rude puppy off and maybe put teeth and pin the pup down but pup should not be hurt. How adept are you at reading dog body language?
OP didn't specify exactly what happened. But you can see how when the average person's smaller dog gets pinned down by a larger one they are understandably upset. I hate to say it....sigh. But it often depends on the dog park. Yes it's possible that a pup can inadvertently elicit/invite a bite. But we've also seen baaaaaad/negligent dog owners that let their poorly trained/untrained dogs run amok. If these types of people are at the dog park in question....best to change dog parks imo.