Going by your description of the feathers cut off straight, there is a scenario where this could occur. Yes, a malicious human who has a grudge against you could have entered the yard and scissored off the rooster's tail. But a predator could have done the same thing.
Is your yard totally fenced and gated? Could a large dog have gotten in? Can you see where any of the tail feathers have been yanked completely out? Any featherless spaces with skin exposed?
Long ago, I had two roosters and I was always trying to keep them from killing each other. They occupied the same coop with a partition down the middle. I would leave one coop door open at a time so one rooster was always able to come and go. One day, I came out and found the outside rooster with most of his tail feathers missing. I figured a bear had come by and seen the rooster exposed and taken advantage. Luckily, the rooster was uninjured.
Unless you have in mind someone you know who wants revenge on you for something, that scenario seems too unlikely. Dogs at large, on the other hand, are all too common, in fact, they are the most common chicken predator besides hawks. A much more likely scenario is a large dog chasing your rooster and he took a big bite out of his tail trying to catch him and eat him.
