Before Yom Kippur I did kaporos with a rooster. While I was waving the rooster around my head for the second time, the rooster tried to get away. I held him tightly and he arched his neck suddenly and apparently he broke it because his neck was bent forward and he was dead. The Rav wasn’t sure whether I had to do it over so I did it over to be on the safe side. Was I required to do it over?
It seems that you did the right thing to do it over. The custom of kaparos comes from kabbalistic sources, which highlight that the slaughter of the bird is a part of the procedure (this is prominent in the writings of the Arizal).
In your case, the rooster was not slaughtered but rather killed, and therefore part of the process is lacking. I would have also recommended, under the circumstances, to repeat the kaparos procedure.