The previous copy of this footage that I saw, made it difficult to clearly see the shirt this guy is wearing. It looks like he is wearing a sweatshirt over a tee shirt. With regard to the guys that were laying flooring/plywood on the 6th floor that day, a sweatshirt would be fitting attire. When they Zoom in on this guy, it appears he is talking. His jabbering would fit if he were simultaneously being asked different questions by different members of law enforcement. Possible questions coming from different sources would also fit his head rotation.
A sweat shirt? when some employees were working in their Tee shirts?......But do agree that the guy seems to be wearing two shirts..... a Tee shirt and another shirt.
The film clip is very brief....and it MAY have been taken before the rifle was discovered...... The guy seems to be very nervous and is watching to see who came up the stairs behind him. The brightly lit windows over the man's right shoulder are the windows that were in the
west NORTH wall at the top of the stairs in the NW corner of the sixth floor. ( The west elevator is visible) But Boone needed a flashlight to see down at the bottom of the chasm of boxes when he spotted a small portion of the butt of the carcano which was lying ON THE FLOOR ( not jammed between boxes of books) Perhaps tall guy knew the rifle was there and was nervous about it being found.