Shooting through the building windows? Extremely unlikely. Review the so called Sniper Nest photo below and we see oodles of blockage. There are films of the east side of the TSBD that show the 6th fl windows to have been shut.
I am only saying that the trajectory could be the same if fired from the Dal Tex through the 6th floor alleged SN window, and it appears that the limo would have been visible through those two windows, that is if the obstacles filmed in the photo provided, which is pre shots, were out of the way.
It is also very possible that the car was visible and more importantly lined up at the time of the last shot.
Only one or two boxes would need to be moved and the most Southern window could have been momentarily opened too, by who ever threw the elevator switches, two or three guys working together would easily plant the hulls and all
This is a huge addition to the case and needs to be debunked, accordingly.