I have no dog in this debate and think it’s generally a fools errand without more data. I’ve stayed out of the discussion so far because it’s just not possible to know these unknowable things without more data so it’s “unknowable” at this point.
Thus far the shot could have come from about 120 degrees S or SE (most likely, 4 likely options), or from the 2nd story NW windows (no evidence of this, least likely).
Crooks could have been holding the rifle in a 90 degree angle perpendicular to his body and the shot could come from is direct front, such as moving the rifle to adjust his position, or perhaps doing an administrative action on the weapon, etc. Shot could come from the South, missing him.
Crooks could have been facing S but had the rifle pointed East, or West, in trying to move or look for an escape or ducking, moving. For instance hold the rifle in a shooting position mimicking Crooks, the point the rifle to your left (East) but look to the right (West). This puts the stock right in front of the likely mouth entry.
Or he was West, pointing the rifle at the crowd as seen on video, and the shot came from the South and winged the stock, missing him entirely. Or shot thru him and hit the stock upon exit.
Or in the prone, angled slightly up, facing S but with the rifle buttstock shouldered high, a bullet fired from the S or SE could glace off the upper rear stock, shattering it, but missing Crooks entirely.
It’s possible or likely he was adjusting, rolling, moving, ducking, moving the rifle, and the rifle was momentarily in between the counter-sniper and his head with the rifle struck on headshot entry, or behind the exit wound, and was damaged either during exit.