really right now there's a steady drumbeat from them calling for these kinds of attacks. you wi all you basically need is a vehicle, and you can, unfortunately, kill a lot of people. security services on both sides of the atlantic are just really concerned about this threat stream. particularly, in the u.k. because in the u.k. there's much less access to firearms. there hasn't been this big threat of a ak-47 style attack that you have seen in europe. that is a plot to rely on other means, and, of course, a car can be very deadly. >> stand by. i want to bring in will. he is a national security and terrorism expert.