What the f*** do you care?? They sing like gods!!

The pictures of the brother, as the mother speaks of him, seem to show us the past. Almost as if it is revealing his growth as a human being until it shows us the most recent picture, even though he will look differently when he is shown in the next few scenes.
Also, after Danila has killed the 2 men in the apartment in order to save the 'weakling's' life, he wipes his palm on his pants, as if he is trying to cleanse himself of their blood, both physically and mentally. He knows how to kill and he does it well, but he never harms an innocent person and only harms in order to protect the innocent. In this regard, he does not necessarily want their blood on his hands, and may be trying to rid himself of this.
The irony of something else struck me. Throughout the movie, Danila is constantly looking for the same cd by Nautilus. His cd player seems to help him think and it is the source of everything for him. He relies on music even in the apartment when they are waiting for the man to get home. This is why it is so significant that the cd player saves his life when he is shot at. The one thing that he has chosen to rely on and turn to in a sense, has been the only thing to save his life.
In the end, Danila chooses to go to Moscow, which is a tad humorous, because it was always his brother who said that the better life was in Moscow. It is at this time, that he takes his brother's advice after telling his brother what to do and who he will be instead of killing.