donna friesen covers the story as a correspondent for nbc news. >> these are not suicide bombers.they are backpacks placed inside the train by terrorists who placed them and then got off the train and left them. there were virtually 25 pounds of explosives in each backpack filled with nails and screws and various shrapnel so there would be maximum damage when they exploded. they were all detonated by cell phones, so they all had cell phones in them and the perpetrators then dialed the numbers of the cell phones. >> marin is standing in the same train car holding one of the backpacks. shortly after one of the explosions knocked him unconscious, he began to come to his senses. >> translator: i started to feel the pain of not being able to move. i was paralyzed. my body was almost totally burned. i could only move my right arm. i was feeling the pain of not being able to breathe because my lungs had collapsed. my face had also been burned. and amid other people's blood, my own blood, the skin that fell on top of my eyes, i saw everything in shades of black or red. i had no sensation