Although it sounds excessive, and it does, my uncle's a cop and he said when you shoot someone in a situation like that you aren't counting either yours or your colleagues shots. Which is obvious, but I mean if you think he poses a serious threat you'll probably unload on them, so will your colleagues, they can't just rely on someone else taking them down. You have to be sure that you've taken them down. This is actually quite common, the only reason this made such a big noise in the media is that the perp was innocent.