far. that may change in the hours ahead. what isis have been calling on their recruits to do as well as launch these kind of truck attacks is actually leave some kind of note, some kind of claim of responsibility behind so that they attach this to some kind of a terrorist group. if german officials have found something like that, they have certainly not revealed that yet to the public. >> phil, there's a lot of questions here because you heard fred pleitgen's reporting, they found a man, a body in the passenger seat of this truck but not in the driver's seat. they're questioning a man they found a few blocks away that may have been the driver but don't at this point which leaves open the possibility this person could be on the run. there's a lot we don't know at this moment. >> that's right. the first question is not what happened in this case, if you're an investigator, erin. finding that person is critical, not to talk to him about the attack. you got three questions for him. number one, are there other perpetrators involved and do they have another plot that they want to unleash within the next day or two?