in nice last year, 86 people died. in this particular instance, it may turn out to be 13 or 14, so significantly less. you want to prevent the people from doing this in the first place because once people get into the van, it is very difficult to stop them. >> peter, thank you. in the midst of all of this, what's been unfolding in barcelona, the president of united states took to twitter, first condemned the attack. and then this. "study what general pershing of the united states did to terrorists when caught. there was no more radical islamic terror for 35 years." so, now you have the commander in chief telling people to study a military incident that historians have debunked as a myth. a myth. tim, presidential historian, what was he thinking with this tweet? >> oh -- believe me, brooke, don't ask me what the president's thinking when he's tweeting except it's clear that