You probably got that already covered but if not:
Here is the most early close up screenshot from the shooters weapon on the roof. Taken just after the first group of 4 made it ontop AGR6 (BWC2-122110).
I’m no weapon expert but maybe it helps specifying/confirming the shooters weapon regarding the audio analysis of shots 1-8. Maybe somebody can make out if the statement in Higgins preliminary, "Shot 9 hit Crooks’ rifle stock and fragged his face/neck/right shoulder area from the stock breaking up.” is accurate.
and zoomed in
The moment when the first group of 4 reaches the AGR6 roof, can also be seen from a position beside the northern crane holding up the big flag (BWC2-122104 => be aware: the timestamp in this video is wrong +12 seconds). I believe you can even spot when they dislocate the shooters weapon. Watch the roof between timestamp 18:16:49 and 18:17:20 (so in reality 18:16:37 - 18:17:08). That also matches with the timestamp in BWC2-122110