I agree, Silverleaf. The killer was smart, obviously, but we can safely assume that kind of assault requires a lot of training and practice. Combine that with the extreme cost of the firearms, ammunition, armor, etc., this appears at first glance to be a very well-funded and well-planned paramilitary operation. I can’t imagine he was acting alone in this horrible massacre.
We cannot safely assume. It my experience, it does not take a lot of training to operate an AR-15 or a 40cal Glock. You could learn to load and fire either of these weapons in about five minutes. Nothing hard about insert magazine, pull charging handle and pull trigger. Same with Glock, substitute rack slide for charging handle. Guns are not complicated machines. They are in many ways simple. As for shooting and aiming, the worst shot in the world would cause mayhem in a crowded movie theatre.
Sometimes the simplest explanations are the correct ones. Here an evil maniac opened fire in a crowded movie theatre for the reason only the maniac knows. No conspiracies, no paramilitary training, no politics involved.