Why do people enjoy making people suffer?

OK this guy that I know likes making other people cry. He actualy tries to make people depresed one time he broke up my best friend with her boyfriend and when she was crying he walked over and goes awww to bad I guess U will get over it. Then the next day he tried to ask her out she turned him down and he got beat up by her X boyfriend and then we made him cry by telling his girlfriend of 3 years that he had been playing around with other girls. So now everybodys happy but him!!My question is why do people enjoy acting like this?