catch up and stop these guys, to prevent them from -- now the one survivor, to stop him from striking again, after that horrible attack during the marathon. you'll look at that video. as pete and i have -- it's been described to us, the white hatted suspect walking through the crowd to get into the front row. calmly doing it. sets down the backpack. watches the other explosion go off. he just sort of meanders away waiting. and then seconds later the second bomb went off killing and injuring so many. >> we keep talking about tamerlan tsarnaev, the 26-year-old older brother, who's now deceased. was there any evidence the one still on the run, 19-year-old dzhokhar, do we believe he was purely influenced by his older brother? unclear about the influence. once he came to the united