OK, the first thing, calm down.
The more you panic, the worse things will get. And if you aren't under any attack, then panicking about being under attack, is going to attract,some bad stuff.
That said, for spirits appearances can change, especially as they're filtered through the monkey mind. The bull-like appearance could tell us nothing, or everything about it.
That said, could you share any other details about your encounter?
Any impressions, emotions, thoughts, that you may have felt,heard or experienced while engaging with this beast?
Go back to your garden. Is it still there?
I can look into it later if you want. Last time I looked into something like this for a member here, I made a new spirit friend.