Dunno. Pretty sure its officer discretion as to which weapons they decide to use. Not all have tasers. Some may have pepper sprays. I do wonder why he didnt pull the taser though first.
Without having been there ...all we can do is speculate...I’m positive the officer is not pleased in ANY way that he felt that he had to use deadly force. Sometimes tazers don’t stop persons on certain drugs etcc....just a thought?