well, they were 2 psychopaths in different classes.
the first one was paul, with 15 years when I met him, he is tall, handsome and strong, the best in sports and incredibly smart
he was new at our classroom and initially kept distant but at the next day he has a lot of friends. he always seems to be concentrating or interested on something, like a lion hunting
http://www.wildlife-pictures-online.com/image-files/lion_knp-0130m.jpg
his face expression is these almost all of the time except when he is with his friends. oh yes, he is very social with a narcissistic attitude, he likes all focus on him but he is not an attention whore
he often plays fighting with his friends and with the girls. he grab them and hit them but he do it with a smile in his face so it looks like a game. he is not grumpy of angry but there are a kid in the same classroom which is bullied by everyone (he is an attention whore and a #######1) including by paul
one day we had to make a presentation and everyone gets nervous doing it excluding paul, he explained it perfectly without leaving any detail and his hands wasn't shaking at all

the second one is not exactly a psychopath, seems like a sociopath. his name is mauro and he is 17 or 16, he it tall, handsome, strong and he is very good at sports too. he is not the smartest and he is repeating study this year (I don't know how do you call it in inglish). he is very talkative and extroverted, he likes watching bloody photos but he is not fearless like paul, we had to do a presentation too and his hands were shaking a little. he is cold/angry/negattive attitude, call it as you like, but at the sime time he laughts a lot and at everyone