Not that it is connected to the assassination, but Why is there a door where the stairwell empties/dead ends onto the 2nd Floor? If there was a fire inside the TSBD and people on the upper floors were attempting to exit the building via that stairwell, this 2nd Floor Door would essentially make the stairwell close to a Gas Chamber. There is No Door where the stairwell empties/dead ends onto the 6th Floor. That 2nd Floor door accessing the stairwell makes no sense.