depending on the department, there isn't much more training required to become a cop. I know because my husband was one. In some states, you can actually serve as a LEO for a year before you are required to have ANY training. After that, most departments require you to go to the range once every few years. Just like a CCW holder, it is up to the individual officer to hone their own skills with their weapons. Some will be dedicated enough to train on their own and others will do what is required - no more, no less.
A few years ago, a fugitive from MA killed a police officer here in Gassville AR. When he was finally surrounded, they fired dozens of rounds of ammo at him (almost a dozen officers had his car surrounded). He died because he shot himself in the head. Not one officer got a bullet into him, only a few rounds even hit the car!!