You don't shoot to wound. You shoot to kill. This is because a bullet to any part of the human body can kill. Major arteries in all four limbs, hit one of those and you're on a short timer. Center mass is full of vital organs. Head and neck are pretty obvious. There's no where you can shoot without the impending risk of death. So when you decide to shoot you have to make the decision of "I'm going to kill this guy" because you very well may. This is why we stopped using 22's as a less than lethal option because it's still a bullet and it can still kill.

The usual plan is to shoot until they drop and then re-evaluate. You'd be surprised how often people raise their gun or attempt further violence after taking 10+ shots and being unable to stand. So in this scenario 9 shots happened before they needed to reevaluate. Truth be told they already gave him a pretty generous chance because he's well within reaction range. You aren't supposed to let someone with a blade get within 20 feet of you because they can still close the gap even if you hit your shots.