Let's say the have the ballistics and evidence that he shot the rounds. Will you believe the evidence or just go the next step and say "why should we believe them, they lie all of the time?". Its a valid point you would bring up but where does it stop?
My hypothesis is that he did shoot rounds 4 - 8. Round 9 was pretty delayed but was a kill shot on him.
Rounds 1 -3 might have come from the two-story window.
If there is video showing the shooter popping off the rounds then things would be settled in my mind.
As it is, the "signature" of 1 - 3 seems to be different, as the podium mic pics them up supersonic speed after they go by, than 4 - 8. Shot 9 was definitely suppressed - which the sharpshooters had. Guessing the prone sharpshooter took him out.