seen in afghanistan, and frequently used there, that is not to say that authorities have come to any kinds of conclusion abouts who built these bombs or where they came from. there is also the kind of work underway right now, we wanted to tell you about the fbi is honing in on the cell few towers in the vicinity of the finish line. the cell towers could have carried some kind of a signal from a cellphone that would have triggered these explosions. if they can establish that as fact that will help them a great deal toward figuring out who left those bombs there. in the meantime, many eyewitnesses are telling their stories today. one of the runners, just crossing the finish line was u.s. army reserves captain tom ken aoerbgs he's just back from -- kenny, he's just back from serving in afghanistan. captain kenny had just crossed the finish line was about 50 feet away from the blast when the first blast went off. lucas carr is a former army ranger who finished the race and