I did monitor carefully the Russian news the days after the assassination, I wanted to know how long it would take Putin to react. It took him a few days, until he just couldn't ignore it any more.

Why doesn't he just go get whomever is involved ? Wouldn't he have a lot to gain from appearing as restoring order and a semblance of justice in Russia ? Why does he never brings those thugs to justice ?

So I wouldn't bet he is a white knight there. He just has too tight a control on things there to be totally ignorant of what went on.