The slanted object in the window is an artifact from the morphing "restoration" of assassination films done for "JFK: The Lost Bullet".
In trying to eliminate the blotches caused by heat damage to the Hughes film, they used a process to smooth out the sharp edges. Ironically, a slanted rifle-like object appears in the window about where one might expect it to be if there was a rifle there. It's still quite a find for something briefly-appearing in an animation.
I find "The Lost Bullet" restoration worked well for motion transitions and eliminated much of the blur and damage. The restorations just don't stand up to frame-by-frame analysis.