There's no single word to describe how I feel about this. On the other hand I'm sad that people had to die (again) for something completely meaningless. And on the other hand I'm sort of happy that it happened in Bruxelles, hitting close the MEPs. Perhaps we'll now see something more rapid and sensible about this forced immigration issue?
One can prevent people from radicalising. It is not an inborn trait, even if some politicians say otherwise.
I don't think there's a 100 % effective method. There's an old saying in Finnish, which goes like: violence is rarely the working option, but when it is, it is also the only right option. Which refers to people you just can't reason with.
Since I know folk wisdom is not on high scientific basis around here, my suggestion would be the following:
1) When caught in preparing the act, don't throw the would-be martyrs in jail. Declare them clinically insane (well, they are if they are planning something like that) and throw them to asylum, preferably for the rest of their lives. Film their lives and broadcast to outside world, preferably after some years of treatments and sedatives.
2) Bury the suicide bombers with pig carcasses. Any little doubt in their minds helps.
3) Criminally charge those people who did not alert the authorities of preparation of the terrorist attack. There's already laws in place for this, the only thing that needs to be done is to implement them as it was done before. It doesn't matter you'll need to investigate the actions of couple of hundred people (in the worst case); in reality the worst case is not to do anything about their inaction and telling them hiding this sort of activity from the officials is somehow acceptable. If they don't have nationality, expel. If they acquired nationality, or are born in the country, then the verdict is significant time in jail, like 15-20 years.
4) Offer significant cash rewards and protection for those who expose the jihadists.
Of course, the above has to hold pretty much for everybody so that the muslim population doesn't feel singled out. But hey, if they commit more crimes, then it's their fault as the same rules apply for everybody.