moment, and that's what a lot of that disturbing video that's been captured actually shows. it is difficult to imagine how terrifying it was to witness all of that unfold but this was a busy friday afternoon in central london, a lot of people saw it happen. take a listen to one account. >> one of my employees had gone to lunch and had been told the building was on lock down and we heard four gunshots and saw people running akrolgs tcross te and after everyone left the bridge the police were going around the bridge and a laurie left in the middle and they started picking up, suspicious and started checking to see they went around the back and tried to open the doors and that's what i saw and in our reception area, we have a telescope where