This is clearly sunlight and it is strange that anyone would even question it? Not only does it look exactly like sunlight should, there are a couple of obvious indicators such as the shadow of the red dog food bag, the grouting between tiles still visible which they wouldnt be if covered up...
The "rifle butt" is actually the shadow of the dog food bag handle, the shadow is in exact proportion to the handle. As the angle of light is a little acute the sides of the handle shadow are a little thinner but still the same length and perspective corrected thickness in relation to each other. The length of the shadow is exactly the same as the side of the dog food bag. The bag is clearly in sunlight as it is brighter than the other bag and no shadows, creases or marks can be seen on its sunlit interior. The wire basket holder behind the bag is also clearly in sunlight, you can see where the light stops and the shadow begins about halfway down the top wire behind the red bag. Compare the colour to the opposite side of the wire basket holder which is completely in shadow and it is clear one side is lighter than the other. Anything in light is going to cast a shadow, and sure enough there is a shadow that corresponds exactly to the items in sunslight and lies exactly where you would expect it to given the light source.
Having said all that I dont think this in any way has any significance to anything in this case. At least I hope not because if a hypothesis requires that this not be sunlight, I'm afraid it is doomed to fail.
