Fuck the rocks, get a pole and beat the shit out of that stupid fucker. (the dog, i mean. if the owner comes at you, which he is bound to do because you're beating his stupid ass dog, whack his ass a few times as well)
Or, get a paintball gun and use some frozen paintballs. Keep some paintballs in the freezer, then get them out when you need it. Pop that mutt in the ass, or the head. (The head works best, just because it's funny to scare the shit out of them) Again, if the owner comes after you, pop that motherfucker in the nuts. I bet he won't try it again.
Or... while that goddamn dog is shitting, take its head and stuff it in the shit pile.