Free will of angels and/or the free will of humans?

first of all, let me just stay that I do not believe in the literal truth of angels or, for that matter in “free will”.

I only want to know the answer to research a fantasy book. as far as this question goes, I would like answers in terms of Christian and Jewish belief, as, in the book, Islam and New Age belief systems do not “count” (though I do not explicitly say so).

my question goes as follows: as far as I understand it, humans have free will to do good or evil and this separates us from both animals and angels. (please correct me if I have gotten this wrong.) how, then, could angels have rebelled? answers on a celestial postcard, please.

once again, I don’t believe any of this really happened.