Ok, I'll play along. Unless you believe the cops unholstered his taser and placed it on the ground, chances are it was in his hands. Time taken to raise object that appears to be a gun and shoot someone <= time to unholster and raise weapon to shoot someone. Police need to be proactive in situations like this because being reactive could lead to getting shot.
The article suggests his hands were in his pockets when shot and that police fired the tazer after he was dead. The current rate of police killings indicates something needs to change. Being proactive doesn't mean killing someone each time you feel threatened. This case shows how that can play out. A little more "reactive" is exactly what was needed.
A very similar narrative was built for what happened in Ferguson: eyewitness testimony that the victim was no threat, claims that police assertions amounted to "superhuman powers" for the victim, &c.
Then the DOJ report more or less refuted all of those eyewitness claims.
The police were called to the scene based on a report of a subject brandishing a firearm. They found the exact person the report referred to. The subject was indeed armed (though not with a firearm). They did not need to tamper with evidence. They didn't need to fire the taser. In fact, doing so would only put them at risk, if they somehow managed to screw up firing it themselves.
