That's dreadful, I'm sure you're right about the dog being relevant sadly.
I have only ever been threatened by a horse once, years ago, when I crossed a large sloping field and didn't realise there was a mare and foal ahead of me, and a stallion behind me, which galloped up behind me and started to rear up. Amazingly turning and facing it with a loud "woah" (seriously?) was enough to stop it, but I have been wary of horses since then.