Lt. J. C. Day and Det Robert Studebaker both testified the photos were taken before the rifle was moved.
Here's Studebaker Exhibit C 
Let's let the photos do the talking...They don't lie, but the DPD cops have been shown to be a pack of liars....
Here's Studebaker Exhibit C

There can be no doubt that some boxes were moved ...because the boxes in this photo do NOT correlate with Boone's description. Boone said that the rifle was at the bottom of a cavern of book boxes.( he shined his flashlight down onto the floor) and saw a tiny portion of the BUTT ( not the muzzle as seen in the photo) of the rifle.
So since Boone indicated that the rifle was completely covered by the boxes that formed the roof of the cavern ..HOW could an escaping assassin have dashed by and dumped the rifle and the dashed down the stairs to arrive just 1 second ahead of Baker?
Answer that question Chappie....