As ever, as the dust settles, the facts become clearer. In the case of Mohamed Merah, the killer of three Jewish children, a rabbi and three soldiers in France earlier this month, the questions have become sharper too.
Though local authorities have been praised for their handling of the bloody dénoument of Merah's short-lived terrorist career, many doubts remain. How many other Merahs might there be? Is this a French problem or a Europe-wide threat? What can security agencies do to make communities safer?
The first point to make is that France has no particular vulnerability to extremist violence, despite the often noisy debate in the country over issues such as overt displays of religious faith in public institutions and the large Muslim population.
Indeed, not only has France avoided any significant mass-casualty attacks of the types seen in Spain and Britain in 2004 and 2005 respectively, but it has produced proportionately fewer of the militant volunteers than other European countries in the late 1990s and the decade following the 9/11 attacks.
That there is now a structurally high level of antisemitism, which often translates into violence, is undeniable. That conservative strands of Islam have made significant inroads in recent years is also without doubt. Yet France's numerous and varied Muslim communities have not shown the levels of radicalisation seen elsewhere. When they look at the Continent, British secret services are currently most concerned about Germany.
But this is cold comfort. Mohammed Merah, juvenile delinquent and mechanic, was, after all, from Toulouse. That he existed at all indicates how ubiquitous the threat is, particularly to Jews, from Lisbon to Tallinn.
Another apparently worrying element is that Merah was not a true "lone wolf", an independent operator with no connections to anyone else.
Though the extent of any training or radicalisation while in Pakistan or Afghanistan is unclear - and may simply be his own fantasy - it is clear that Merah was plugged into extremist networks in and around his home town. Terrorism is, at least in terms of its mechanics if not morals, a social activity like any other, and there has been no case yet of a militant being entirely divorced from some kind of group dynamic which has at the very least encouraged him to think he were doing something that someone would regard as praiseworthy. Merah's brother has reportedly told the police that he was "proud" of his sibling's actions. The reactions of the various other low-level activists with whom Merah was in contact are unknown but can easily be guessed.
But the "networked" nature of modern militancy holds out the best chance for stopping such attacks. A genuine "lone wolf" would be almost impossible to detect.
The French security services have done a decent job over the past 15 years of keeping the Jewish community safe. They will now be examining how Merah was allowed to amass a potent arsenal, escape detection
In the UK in recent years, their counterparts have been able to identify many potential attackers through working closely with local police and local communities. This approach, long sniffed-at in France, where a more coercive model has been favoured, has been of critical importance in tracing out the crucial small networks.
Coupled with enhanced powers and more resources, the threat has been mitigated, if not eradicated, in the UK. The British have learned much from the French over recent years.
Now the cross-channel flow of expertise should be reversed.
Jason Burke is the author of 'Al Qaeda: the true story of radical Islam' and, most recently, 'The 9/11 Wars'