From Ayaan Hirsi Ali:

In a liberal society, it is appealing to think of suspects of Islamist terror as solitary actors. As a matter of principle, we uphold the importance of individual freedoms, rights, and responsibilities, while our judicial system assumes that individuals are responsible for their actions. We also recognise the importance of not maligning an entire community because of the extremist views of a few of their fellow believers. This is particularly crucial when the historical relationship between a particular minority and their new country is fraught with memories of colonialism.

But while individuals responsible for terrorist attacks may conduct their attacks alone, they still emerge out of communities or networks of like-minded individuals, whether in-person or online. They learn from teachers, imams or instructors the radical ideas that inspire their violence. This is not to say that their entire family or community is extremist — only that these individuals find and are exposed to people who are. Little is known about the background of the murder suspect, Ali, but we can be certain that if found guilty, he would not have plunged a knife into a total stranger, possibly picked at random, wholly of his own accord. Someone or some group would have inspired these actions.