A grunt is usually made by a buck on a doe, or on a hot trail from my experience. I think they thought they would get "lucky". A buck can breed biologically year round, but as you get in cooler weather climates, the timing gets more concise, "rut". You my be closer to the rut than you think this year?
In any event, I bet that was exhilarating having them come like that, I always get tickled when you can do that, or rattle them in, of course in this case, you where trying to run them off, most fellas get the opposite effect most of the time.