Is it normal to have an orgasm without having sex

Well, I am a 21 yearold Student studying at a university.I once had a class taught by an outrageously attractive proffessor, i couldnt help it , but when he passed by my chair and i took a look at his sack i started to orgasm, i dont know if this is normal ? It is a HUGE embarasment to me especially since the class was filled with students. After the orgasm , which was characterized by toe curling and some moans , he started staring between my legs. ! I think im abnormal ! what do you think ? What do you think ,he might think about me ?