Boston Bomber "Trapped" By Phone?

"...The video obtained by the FBI captures this man using his cellphone at the moment the first explosion detonated 100 yards away on Boylston Street on Monday and 12 seconds before the second blast close to where he is standing...  Federal agents then focused on the time-frame of that conversation to retrieve cell-phone records to identify potential callers according to CBS News....Call logs were then obtained through the cell phone masts surrounding the attack zone and using these, investigators matched up the users' identity with the time specific video and pictures to zero in on the individual...