this year which killed a number people in the swedish capital. there is a pattern of you see becks getting involved in these attacks. there was one in 2007 against a u.s. air force base, the ram stein base in germany that linked back to you sthem. >> in terms of vehicle attacks like this, it's very difficult, obviously, to prevent these sorts of things. >> unless we plan to turn ourselves into some sort of prison system where anywhere where there's large crowds and vehicles able to access them that we're going to cut them off. we're not going to do that. it can't happen in new york city or any crowded western city. the way to stop these attacks is the fbi has done a study of