The problem isn't taking it. How do you stop it?
I don't know. This is over 200 casualties with a stupid truck. Not a bomb, not an assault rifle, but a truck. It's too late to freeze all Muslim immigration; they're already there. Intensive communications monitoring will only take you so far. A huge effort has to be launched, the procedures of which I no not, but which I imagine citizens right to privacy isn't a priority in.