Knowing how toxic this community usually is, I'm sure I'll regret posting this but here we go.
Having been in many situations like this before, both from the military side and on the law enforcement side, I can tell you firsthand that the stress and adrenaline levels are about as high as they can possibly be. Being able to remain calm and collected while being ready to react at a moment's notice is very hard and is learned through a lot of training and experience.
That being said: As an admittedly hot take, I do not think this officer had the right mindset, training or demeanor to be in law enforcement. There are also far better ways to go about controlling a given subject and situation. Getting the subject's hands in the air, having him slowly lift his shirt and turn in a complete circle (to ensure there was not a firearm in the waistline), and then walk slowly backward toward the officers, with his hands in the air and elbows locked out, where he could be cuffed and searched, would have been a far more effective tactic.
I can tell you that at the federal level, while we are trained to treat every encounter as potentially fatal, it is also standard practice to deescalate as best we can.
To all the cop haters painting all law enforcement as power-hungry murderers, all I can say is that you are very, very wrong. The men and women that I work with could not be more professional, courteous and diverse. We are made up of every race, religion, gender, sexual preference and background. All are highly educated, and all take the responsibility of the power we are given seriously.
There are no redneck racist militia wannabes, and there isn't a place for them. Nobody is just "itching for a kill", and when we have to make an arrest, it is planned in the way that is most likely to avoid a violent confrontation.
Unfortunately for street cops, they often don't get the benefit of planning everything out well ahead of time. They have to make a lot of snap judgements and tough calls in bad circumstances. In a lot of cases they don't always get the same high level of training.
So I guess what I'm trying to say is, I think the officer fucked up but stress was high and he shouldn't have been there in the first place. Punishment probably should have been more severe. There are shitheads in every organization or group of people, but they need to be weeded out. You cannot paint everyone with sweeping generalizations.