Is it wrong to embarrass a bully?

There is this kid that bullied my friend last year in the 7th grade . It really pissed me off. I was riding my bike down the street and I saw him getting beat up in the middle of the road. So I took out my Phone and filmed it. So the question is, would it be wrong to post the video online. I live in Houston, and bullying is really bad here. I know that you are going to say that I am just as bad as he is, but he really bullied my friend bad last year. I finally have some dirt on him, and I want him to go through what he did to my friend. If I do post this video, will this stop him?