Time lapse taken following the Boston Marathon bombing


The small package on the ground behind the blue fence in the lower left (right in front of the VIP section) is most interesting.  Note signalman at 2:02 as he backs up and flashes a light when he's in position.  There is an awful lot to be seen in 4:43 of time lapse video, including some of the "victims" as they exit the set.  Note that the ambulances were sequestered several blocks away and never deployed.