Across the street view of the incident, shows just how quickly the cop had to react.
https://mobile.twitter.com/i/web/status/1385305451428990978
Interesting video. Not sure what happened before the video, but the confrontation escalated AFTER the cop showed up. I know if the cops every showed up at my house I would be real quick to calm myself down “Yeah (with my hands up) - we’re all cool now, just a little friendly argument...” rather than attacking two people right in front of the cop.
Also - how fast did that cop have to transition from a hand fight (trying to get the girl off the other person on the ground) to shooting her to stop a deadly threat!? AND - the presence of mind to notice the difference!