That graphic is very interesting. It shows the angle from the southern Hercules team is just right so that a shot from them might pass enter the left side of the suspect’s face, exit his right lower side, and then come very near to his right knee.
If the suspect was laying prone, then I think a bullet would pass over and miss the knee. But the suspect turned to his right and faced west for a moment as the following photo shows. (The caption is incorrect insofar as it says he is facing north.)
The photo does not show it clearly, but in this half erect position it would be very natural to flex both legs and for the right knee to be raised up (perhaps 24 inches). And in this position it might be high enough for a bullet from the southern Hercules team to clear the roof ridge vent, pass through his head and then pass through his knee.
My main reservation about this thesis is that the lower knee wound does not necessarily look like an exit wound.
Notice also that in his half erect position the gun is swiveled around and almost points north. In this position the stock or butt end of the rifle is closest and most exposed to the southern Hercules team so that a bullet from one of them might well first hit the stock and then either penetrate the suspect or send fragments from the stock into his body or both.