Kyle testified that he never "aimed" his weapon at anyone, other than those that got shot, I'm guessing the photo evidence showed something different, and the Pros witness, pretty much shot that right in the ass.
Since I couldn't see, nor make out the video/screen cap that was enlarged, I can only assume that he dropped the extinguisher, probably adjusted his rifle, because that was about the same time he started getting chased by Rosenbaum.
That's what the drone footage supposedly showed was that he aimed the rifle at the Zimenskis, but as stated, he may have just adjusted the rifle because that was when Rosenbaum started the chase. Then again, Kyle did testify to yellowpants having the pistol in hand when he started getting pursued. May have been something Kyle don't recall, who knows. Give that kid credit for the beating he took on the stand, just wish the defense would have prepped him to use the term "deter/deterence" more, and use "I don't recall"; seems there were times he agreed to things that he wasn't exactly clear on.