blacking out from anger

ok this has never happend to me before... at least not in this since. ive never been in an actaul fight before in my life and have never really been a very easy person to get extreamly pissed off to where ill hit you. and matter afact ive never hit anyone up until now. im 19 and im beign charged with something that i dont remember doing. i mean i know i did it, but i dont remember doing it. im being charged with assult and battery for hitting this guy that 1. even said that he deserved me hittin him and should have gotten more...and 2. i knew he deserved it plus some. but this guy used me to get back at someone else and i found out about it and it pissed me off. i remember getting in his face and yelling and screaming at him and then the next thing i remember is his glasses flying off his face and me walking away. i didnt know what i had done. i knew as i was walking away that i had to have hit him, but when i didnt know... how many times i didnt know... but as i started to calm down my hand started hurting and thats when i really knew i had hit him. im just trying to find out if anyone out there has had this problem as well.