I was cat sitting for a friend when his cat got attacked by a mockingbird. This cat was only let outside with supervision, and he never left the yard. This mockingbird had been harassing people in the area as well as pets; it was not defending a nest (winter, no nests around in trees or on houses), it was just attacking things for no good reason. This poor orange tabby couldn't deal with the bloody thing and was starting to not want to go outside.
The next time the little bugger decided to come down and annoy the cat, I shot it down with the garden hose. The cat took care of matters after that.
LOL, I live in Texas; it's our State Bird and I could get arrested for that.
When I was in college, we had a rogue mockingbird that was attacking people as they walked by. After about the third time, I was ready for it, and kept one eye on my shadow while I walked to class. When I saw the the bird's shadow swooping down, I whirled with my spiral notebook and bopped it, but not hard enough to hurt it. It fell to the ground, but took off quickly. It didn't bother me any more after that.
Mockingbirds can turn bad. You did the right thing!