dr. david, who heard the shots and ended up reporting to work and seeing what we now know as suspect one. kerry sanders was among those on our team originally assigned to this story in boston. then came word of the cop shot in cambridge, not far from the harvard campus. then came word, shots fired, three explosions in watertown, mass. >> reporter: it's been chaotic since really. arriving in watertown in the aftermath of the explosions and the shootings, the officers were so concentrated on what they were dealing with and i'm talking about more than 100 officers that as a reporter, as bystanders, one guy rode his bike. up to what was going on. right up there just out of curiosity. wasn't really until the officers realized that things had moved into another section of watertown that they could turn around and start pushing people back because they were so concentrated on the suspects. then i went on foot with a camera crew and e we started walking in through some of the neighborhoods and stumbled upon one of areas where there had been an exchange of gunfire. and that is where one witness had been actuall