"Who said anything about me going back!?" Regulus wasn't expecting a fist to the face at all. Sirius had hit him right in the mouth. And he hit the floor. Regulus already had a busted lip, wiping at his mouth he looked at the blood on his hand. Now he was seeing red, literally.
Regulus charged after Sirius, throwing his arms around his middle using his leverage off the ground to take him down.