H.A. Hellyer is a non-resident fellow at the Centre for Middle East Policy at the Brookings Institution in Washington, D.C., and in International Security Studies at the Royal United Services Institute in London. He is the author of Muslims of Europe: the 'Other' Europeans.

Perhaps it was only a matter of time. As the news broke about the shooting in Ottawa, my mind went back to London in 2005, after the July 7 bombings there. The phenomenon of radical Islamist terrorism from among Western citizens has been a threat to Western communities for years – and while Canada has thus far been spared from it, that era is over. The question is where to go from here – and where not to go, in order to ensure that Canada remains secure not simply in national security, but in its fundamental values, as well.

It was almost a decade ago that I was in England when the London bombings took place. As Britons, we wondered: What happened? How was it possible that British citizens could take aim at their own and kill in pursuit of a political objective? As deputy convenor of the British government's task force on tackling radicalization and extremism, I saw our top officials, and our average citizen on the street, become confounded by the issue. There was much we learned to do – and much we should never have learned.

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Canadians stand at much the same point today. The tragedy in Ottawa did not take place in a vacuum – and the forces that were in play before this attack remain. There will be those who seek to use this incident for political gain, in a variety of fashions.

For example, there will be those who seek to put a wedge between Muslim Canadians and other Canadians, insisting that the Muslim community at large is a "problem." That Muslims are all susceptible to becoming terrorists, and thus need to be more carefully scrutinized. We saw that in the aftermath of the London bombings – the "securitization" of Muslim communities, where every issue to do with those communities, from housing policy to social integration, could be interpreted in the media through the lens of security. All too slowly, we learned how much this was to our detriment.

There will be others who will try to use these suspicions to prove to Muslim Canadians that they can never truly be at home in Canada, and that they ought to join the other side. Indeed, when the discourse of Islamic State recruiters on social media is analyzed, many of them continue to argue that Muslims have no real place in Western societies. That they will always be outsiders, and thus that they should migrate to the "true" abode of peace – under the rule of the self-proclaimed ruler of all Muslims, Abu Bakr al-Baghdadi. We needn't validate their theories.

Canadians – all Canadians – have a choice. This kind of extremism cannot be explained in short articles or pithy sentences that reduce and essentialize everything about it to issues around foreign policy, ideology or pseudo-religion. It is complex – because the nature of this extremism, as we found in Britain, is complex. The motivations and factors are disparate, and they vary according to person. At the moment, there is the assumption that the shooter has been motivated by some sort of religious ideology – we haven't yet received confirmation on that – but it is important to keep in mind a number of factors.

There is indeed a neo-religious, radical interpretation of Islam that has been used to justify and motivate this kind of action. It's a vicious ideology that needs to be tackled, and not apologized for. But we know that it has been condemned by many religious figures, including many in Canada. Shaykh Faraz Rabbani, for example, a noted mainstream religious scholar in Toronto, has been clear on this point for years – not just on Wednesday. Credible, authentic religious voices from the Muslim community seldom make it into public discourse, which then leaves us stumbling.

If voices from the Muslim community speak with passionate clarity, but we don't seem to listen, it's not their fault – it's ours. Many will be tempted to take them to task for this atrocity, as though they were somehow in tacit approval – this isn't just unfair; it will divert energies from where they really need to be focused. We have seen this before in other countries, where counterterrorism strategies rely on using energies where they are best deployed, because there is a finite amount of time and effort to be used.

But these won't be the only issues that come to the forefront in explaining the motivations of such individuals. There will be others, depending on the individual in question. For many attracted to such radicalism, ideology is indeed the most critical factor. For others, it is more about politics. For others still, it's a youthful idealism gone astray – and for others still, it's all of the above and more. Rather than focus on one and lose track of the big picture, Canadians and their allies in other countries will need to continue to be broader in their thinking, and calm in their assessments.

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Indeed, initial reports suggest the shooter suffered from mental illness, and had been evicted from his own mosque on account of suspicious behaviour. Such things would appear to be more relevant than, for instance, one broadcaster's observance that the man was wearing a scarf of Palestinian origin in a picture widely distributed online.

The calm attitude displayed by most of the Canadian media on the day of the shooting is an example to the world of how a people under attack can respond. Rather than behaving with reactionary hysteria, Canadians composed themselves admirably. Continuing as such will be their greatest asset.

Canada can either make its Muslim community suffer twice for this attack – first as Canadians who feel pain about what happened, then as Muslims unfairly suspected of collusion – or they can continue to stand with their compatriots against any threat. They can succumb to panic and chip away at their own hard-earned civil liberties under the rubric of a new stage in a "war on terror" – or they can stand fast, and recognize that those liberties and freedoms are precisely what were being targeted on Wednesday.