@Maala : no, I would not ask for five innocents to be killed to get my revenge. Maybe it was the assassin idea to kill the witnesses but the old man was okay for it (he doesn't just allow it, he paid extra for it).
To take his revenge, against someone who broke his family apart, he is okay to kill and broke other families apart... That's not okay.
And previous misfortune can't allow future misdeed. What happened to him is tragic but it doesn't give him a free pass for the next horrible thing he'll do.