It's the drinking. Some people just are mean drunk. Do not get drunk ever again. If you drink just limit to a drink or two and just state that you won't drink anymore due to what happened last time and just stop there. Do this friends drink a lot? Do you?

I see that you contradict yourself in your statements: "I am not mean, I am a good friend, I am a nice person. Don't know where this came from" and then you go on to say you have a history of violence when you were younger... or at least a history of being mean. So you do know where it comes from, and there's more from where that came from. In therapy go through this and the unresolved trauma because your inhibitions disappear when drunk and that's why your mean behavior came back.

As for your friends... you need to apologize profusely. Sit down with every single one of them. Go through the behavior. Accept responsability, say you are going to therapy to address that issue and you are committed to work on this since it was not ok and it hurt people you care about. Finally, offer restitution. How sre you going to make it right by the people you hurt? Maybe some dinner and just go through the whole process of... being in the dog house as it were, since your stunt hurt people. Just be patient with them and with yourself. You made a mistake, a big one but you are a human. Just try to make this right.