The officer was equipped with a P229 Sig Sauer, which loads with either 9mm or .40S&W rounds. I've been unable to find whether the autopsy indicated 9mm or .40 rounds, but if it's 9mm, it's most certainly not true that a single round would stop someone who's charging towards you and is flooded with more adrenaline than they've ever experienced in their life. This phenomenon has been documented time and time again, as counterintuitive as it sounds.
In fatal stabbing incidents, people often comment about how they had no clue how bad the stab really was. That's because adrenaline disables your normal systems which tell your brain that anything is wrong.
Officers aren't trained for Hollywood-style precision shots to the leg. They are trained never to point their guns at anything they're not willing to kill, and if you are forced into a situation where you must use your weapon, to aim for center of mass and continue shooting until the threat is neutralized.
If we disagree with officer training policy, we should try to change it. But we can't go back now and say they shouldn't have followed their training.