"To paraphrase a famous quote, “Never bring a Taser to a knife fight.” The Taser is a single shot device that doesn’t always hit its target and doesn’t always immobilize the target if it does hit. When someone is attacking you with lethal force, you defend yourself with lethal force." Maybe that works if it's just a single officer, with just one hand. But, there's multiple officer involved in this incident, and I'm guessing that they all have more than one hand.
The Taser is held in the same hand as the firearm. It's the officer's decision which one to use. These three officers made the right decision. The alternative is something like
this, or worse (graphic photo).