thing when someone pulled up behind him, knocked on the window got their way inside the car, put a gun to him and told him to drive. he later identified that man as tamerlan tsarnaev. he said right away that man told him he was responsible for the marathon bombing and for killing a cambridge police officer. imagine the terror. interestingly you reported that mang told the defense he never saw dzhokhar with a gun, only tamerlan. how did that play out in the courtroom? reporter: that s are been a point of contention for the defense this entire time they ve been trying to prove as the government brings in these witnesses that tamerlan was the one who was in charge. dzhokhar was influenced by him and was just following along with his older brother. so that goes along to that same point that mang only saw tamerlan with a gun. however, for the first time prosecutors were playing this video. we re going to show dzhokhar in the moments before the bombing walking through the crowd and the