If she was repeatedly warned and continued to attack the other girl then fair dos I guess.
The officer just didn't have much time.
If you watch the whole incident in slow motion the officer approaches the scene, then Ma'khia, knife in hand, rushes the first woman who falls over, she slashes at her as she's on the ground, the man on the scene aims a kick at the floored woman's head.
Lovely!
At this point the officer was saying 'hey hey' then 'get down', 'get down'.
It's unclear when he first see's the knife.
Ma'khia, after flooring the first woman, turns her attention to the woman in pink, she rushes at her, knife ready & the officer must either react or just let what happens happen. He is trained to react.
I believe he acted appropriately & responsibly, a taser may have been ineffective & the threat to life was imminent, there was no other sensible option.
He wasn't excessive in the force used, he shot until she stopped posing a threat & no more.
The shooting in slow motion.https://youtu.be/Fpnibt9RQ2U?t=522