You know, VICE news did a couple of specials on police training, and I can tell you that there are a lot of things that qualify as "training" that police forces spend lots of money on, but it's basically worthless. In one of the training sessions, the instructor got up on stage and told them that shooting someone releases a whole bunch of adrenaline, and if you shoot someone on the job, you will have great sex that night. Yes, he actually said that.
I know that when I went through Security Force training, there were several things that we were taught (and was enforced by the Gunny) as to how to handle our weapons. One of the main ones was ammo control. At the range, we NEVER emptied a full clip into one target. We were taught to shoot 1 to 3 times, assess the target, and THEN and only then would we fire again if necessary. Our range had targets where we had to shoot at them from a doorway, a window, behind a wall, prone, kneeling and standing with a modified Weaver stance. And, you never fired more than 3 shots at any one target. If you did, and didn't have ammo for the last 2 targets, it was considered a fail.
Nope, sorry, but they don't really screen these officers much when they first train them as evidenced by some of the psychos that show up on the news, and the training apparently goes downhill from there.
Why can't we hold our police forces to the same performance levels as the military?