The US had intelligence of a possible attack and warned Americans Wednesday night to stay away from the Kabul , Afghanistan airport.

Today, the military confirms several service members were killed and wounded along with Afghan civilians in an explosion.

The effort to get Americans and Afghan allies out in the next five days it is now even more dangerous. Former FBI agent Jerry Clarks tells us these acts of violence are unpredictable.

Clark said , "Prevention is very difficult at times especially in crime or terrorism. The part we have to be really good at is collecting information intelligence that might lead us to believe this could happen and then acting on it".