I used to do a lot of agency training. The most commonly issued law enforcement handgun in the United States is the Glock 22. It holds 15 rounds of .40 caliber ammo in a magazine. If you do a proper administrative load, you walk out the door with 16 rounds in the pistol... 15 in the mag and one in the chamber. Most cops carry two extra magazines. That gives them 46 rounds when they hit the street. I used to tell classes all the time that if they shoot a guy 46 times and he still poses a threat, call me at the office and I will bring you out a box of ammo and you can reload and we'll stand there and shoot him together until he is no longer a threat, but once he is no longer a threat, we immediately stop shooting him.
Ideally, the threat should be neutralized after the first controlled pair, but reality has a habit of not cooperating with ideal.
As I mentioned earlier, most people have no idea how many rounds they have fired after a confrontation. They don't know until the gun is inspected and someone tells them how many rounds were expended. When that happens, they generally look shocked and say "No way..." Reality is that most people, even cops, unless they are very well trained, fire until the slide locks back.
I don't know anything about this cop, his history on the street or his training, but I am inclined to agree that his lawyer sucked.