I mean in the US there was a mass shooting that killed more the London attack just a few weeks earlier. There were twice as many gun violence deaths in the US than the London attack on the same day (including a baby that shot itself

).
And people treat those as business as usual.. or I guess that's probably not fair, everyone would say they were tragic, but many would also say they're the cost of having a free and open society with gun ownership. Or if you ignore guns and just consider people killed by knives or other ways, again that's the cost, the consequence of having a free and open society.
In a free and open society, some people are going to <insert whatever happens to push them over the line> and kill other people. There's ways to reduce it while maintaining that freedom and openness, but there's always risk. Why, when the thing that happens to push them over the line, is radicalization, is it different than the rest?
I think no matter what you're going to have violence.