My take also. That old ladder against the wall the we learned in school. And he WAS an experienced shooter.
Well, define experienced. That could be basic shooting skills or sharpshooter marksman or a whole lot of other stuff. From what I’ve seen so far, he was experienced enough to load and shoot, and to figure out how to aim. But given the number of jammed weapons the sheriff described, he was not smart enough to exercise his artillary enough to work out defects, ammunition that would not have feed issues, etc. so he might have been book smart, but not highly ‘experienced’.