Tbh, we'll carry on as is, letting the law judge the criminals and the government do their job. There's nothing you can do about preventing all lone-wolf attacks. Compare the murder rates, homegrown extremism, social and economic policies in play and other salient factors that always get dumped below the radar by these threads, and you won't be as terrified. We know why these posts exist in GD, and why tabloids love these stories. It's just a sensationalist circle-jerk using tragedy for an agenda.
Still, say half the people in this thread are one experience away from a rampage, and say they are representative of your broad social group, would you still leave your house? Of course. What are the risks? Well, you're still more likely to be run over by a normally functioning adult in a used car, chatting testicles on the phone when they really shouldn't, than by a Muslamic Fundamentalist Loner Nutter Whatever. We can generalise all night. Treat people as people and diffuse the othering that everyone likes so much. We'll get there in the end.