He HAD to have gotten it, at some point in his life
Another very good point. Where did he learn to shoot and reload? This whole thing points to a well-put-together operation. This guy is an operative. Where did he get the money to buy all of that ordnance with no real job? Hmmmmm???
Not just to shoot and reload - but to do it in full body armor, in the dark, in a closed area saturated with tear gas, while masked!
Ask anyone with military training if this is an operation a first time gun shooter just up and does, managing to shoot 71 targets in the dark, with no training or range practice, with no dry run, based on reading directions from the manual or paying a video game
See #15
Re-weapons training: Note that the shotgun was apparently abandonded. it would be time consuming to re-load for him after he emptied the magazine (5 rounds?) and then did the most firing with AR-15 semi and Glock semi; both of these are magazine fed, thus easier for a novice to reload. Also, based upon the time in the theater, he didn’t bother with reloading magazines; thus he probably had several magazines for the AR and Glocks. In speculating here — perhaps he thought there would be shootout, giving him time to reload mags & shotgun. And 6,000 rounds is a heck of a load to carry into the theater through the back door. It also sounds like some (most?) of the ammo was left in his room. Also, how many rounds would/might he have used up in practicing with the guns.