It's more about how the people you know affect your angle on life. There are four different sides of the story; The Guard (Paul), The Guard's Boss (Keith), The Child (Billy) and Mark.
Paul sees his Boss as a hero and a role model, but sees Mark as a "lowlife psycho", only because he did not know the reason for Mark's actions against the person he looks up to.
Keith sees himself as an authority figure who is well respected and means to do well by teaching proper discipline. However, not knowing of Billy's circumstances, he nicks him the same as he would any other child, presuming that Billy is just another criminal.
Billy just accepts what's given to him from his father and then from Keith, as he also accepts the responsibility for his mothers death, which is why he forgives his father for beating him. He decides not to live after accepting all blame.
Mark lives only for what's to come, and to give his family a good life, especially his little brother, and there isn't anything more important to him. When he finds out that this has been taken from him, he seeks revenge. To him, Keith is a murderer and nothing more.
So the different angles, which are made by who they care for and look up to, change the way they react to the others in the situation.
In summary, I think the main contrast is between Keith and Mark.
From Paul's angle it is Mark who is a murderer and Keith who has been taken from him.
From Mark's angle it is Keith who is a murderer and Billy who has been taken from him.
It's more about how the people you know affect your angle on life. There are four different sides of the story; The Guard (Paul), The Guard's Boss (Keith), The Child (Billy) and Mark. Paul sees his Boss as a hero and a role model, but sees Mark as a "lowlife psycho", only because he did not know the reason for Mark's actions against the person he looks up to. Keith sees himself as an authority figure who is well respected and means to do well by teaching proper discipline. However, not knowing of Billy's circumstances, he nicks him the same as he would any other child, presuming that Billy is just another criminal. Billy just accepts what's given to him from his father and then from Keith, as he also accepts the responsibility for his mothers death, which is why he forgives his father for beating him. He decides not to live after accepting all blame. Mark lives only for what's to come, and to give his family a good life, especially his little brother, and there isn't anything more important to him. When he finds out that this has been taken from him, he seeks revenge. To him, Keith is a murderer and nothing more.
So the different angles, which are made by who they care for and look up to, change the way they react to the others in the situation.
In summary, I think the main contrast is between Keith and Mark.
From Paul's angle it is Mark who is a murderer and Keith who has been taken from him. From Mark's angle it is Keith who is a murderer and Billy who has been taken from him.