A neighbor posted a clear bird's eye view of the shooting and some facts changed. I stand by my conclusion that the cop should've grabbed or thrown Ma’Khia Bryant, but there's key points I missed...
1/ https://twitter.com/IDoTheThinking/status/1384728294709288962

The 911 call, I'm assuming was made by Bryant, where she screams that "these grown girls" are trying to stab her. So, if that's Bryant, its rather clear that she neither instigating the fight nor the stabbing. Remember that when the character assassination comes.
2/

The fighting had ended as the cop pulled up and it appears all 4 involved (2 intruding women, Bryant and a boy) see him but the verbal arguing irritates Bryant and she charges one of the girls. Obvious question: why is this cop alone if we know >3 ppl + knives are present?
3/

The cop rightly grabs Bryant but boy kicks a girl on the ground and distracts him, and lets Bryant, who he saw had a knife, leave his range. Keeping his hand on his pistol to monitor Bryant instead of chasing her, Bryant runs to try to stab the girl in pink before she's shot
3/

*This situation wasn't easy* under the current policing paradigm but if interventionists had taken this up, more than one person would've showed up and priority would've been to separate the fighting parties, as opposed to maintaining a shooter stance and being fairly immobile
4/

This is a classic problem in American policing. From the moment he arrives, it's one guy dealing with 4 people fighting. At this point in the video, only screaming is happening, and yet because he's got no backup, he walks with his hand on his pistol anyways.
5/

Because he's more concerned about his ability to remain in a shooter position and use his pistol, it basically ruins his maneuverability. He couldn't run and grab Ma’Khia Bryant because he's too busy trying to keep feet shoulder-width apart and his pistol ready to be drawn.
6/

A lot of pampered commentators who never grew up in poverty are going to ask why Ma’Khia Bryant decided to fight despite seeing the cop and, fuck them, but esp. when you're a foster youth: your mental health is already severely impaired. You are in survivor mode 24/7.
7/

The 911 call was Bryant asking for help. Now is the time to ask how it could've been given to her other than death. The answer isn't to assassinate the character of a 16 year old girl who life dealt a worse hand than everyone gleefully sharing a video of her death.
end/

Cue the Americans who are so dumb they think the only way to deal with knife crimes is by shooting people. as if the UK doesnt have a knife crime epidemic yet UK police kills only 3 or 5 people a year.

If there's one really dumb police criticism its: "Why does it take so many cops to subdue 1 or 2 people."
Same reason civilian patrols and interventionists go in groups. Multiple people can subdue withou fatal violence. 1 person can't so excessive violence is probable.