Why is he grinning? Because in Europe, Muslim criminals are worshipped like holy saints. He knows that he will receive no significant punishment and may even be rewarded in one way or another. Instead of hanging him, as most normal people would do, Europe will give him money, clean, sharpen, and return his knife, and then apologize for arresting him in the first place.
That is why he is grinning. Because he knows that Europe has become a nation of weak apologetic idiots who fear actually taking a stand against violence more than they fear the violence itself. At most he will be deported, only to return in a month to do it all over again.
Why is he laughing at Europe? Because Europe has become a clown-State full of pusillanimous sycophants who run and bow to kiss the arse of people who rape and kill them.