Reason behind unprovoked attacks as Oneeyevic asked. My personal feeling is that there are few factors behind it.
1 � Family factors- As I said before in the case of that boy got murdered recently in a bakery. His mother is feeling sorry for the parents of the criminal, but I would not be surprised if his parents be proud of him for being tough. Most of these families are where there is no marriage, or wholesale kids from more than one father.
2 � Depression � That could be due to financial, family, social, physical, work related, film and video games related. Could be any thing.
3 � Alcohol � Most of unprovoked attacks are related to this reason and a combination of any other.
4 � Punishment � a good number of people commit crime because they want to show off and are aware that there is no punishment which will make them think twice before doing it only for pleasure. Happy Slapping or whatever they call is the example. They do it only to film it.
5 � Positive activities � Most of the people who are doing are from those areas where teenagers are not busy doing something positive.
I think this is enough.