He was competent with his former service weapon. That is not surprising at all. He transitioned from strong to weak side quite well, used cover correctly and pushed up on his targets aggressively to gain the advantage with aggressive action.
In short, he was at war and his opponents were in shock. He wins. It’s not complicated.
Lesson to take away from this? A gun fight is similar to a knife fight at distance. Being in good physical shape is freakin vital. The cops looked like slow, fat, heavy breathing donut addicts. Couch commandos on the right better run some freakin laps!
He also be dead.
One shooter against a big city's cop squad does not a victory make.
Goal accomplished, perhaps.. but the cop squad remains and he does not.