I pretty much agree with the rest of you. If I'd been one of the women in that apartment, I'd have wanted the person with the gun to do exactly what this guy did. Don't escalate the situation as long as it was just a robbery. But once it became clear that they were going to shoot everybody, don't let the possibility of wounding me keep you from shooting them first.
If the bad guys hadn't been stopped, the wounded woman would probably have been dead.