Chris Sr was shot while he was standing inside the trailer. Remember, the front door was open. He was shot while standing inside the doorway by two different weapons shooting from the outside.
The ME's crucial evidence was noting that he was shot with 2 different bullets, hence 2 different guns. 1 bullet - the one that shattered his arm - was fired from a high powered rifle, either SKS or AR (not sure of initials of high powered rifles, not a gun expert).
All of Chris's wounds were incapacitating, if not fatal. Jake can't argue that he shot with the SK whatever AND another weapon while standing in the yard with GW4 cowering nearby. Two people shot Chris Sr from the front yard with 2 different weapons.
Gary was also shot from outside. That was all made clear in the previous 2 days testimony,