it is now 2:50 p.m., dzokhar raises a phone to his ear, the plan is now in motion. >> what the hell was that? >> tamerlan detonates the first bomb. >> oh, my god! something blew up. >> in the chaos, dzokhar walks quickly away from his backpack. he leaves it on the ground right near 8-year-old martin richard. behind the richards in a blue sweater is 23-year-old lingzi will you. >> she walks into frame right before the first bomb goes off. you see her turn to look toward the finish line where the first