I'm in my armchair, so I'm attempting to do no second guessing.
Guy charges cop with a hammer. The video makes it looks like it was well beyond 21 feet. It appears she got her pistol out, but no shots until he already had her down, or at least just as he swung the hammer. If I was gonna second guess, I would say it appears she could have started firing earlier, but again, I wasn't there.
I can't tell if she hit him multiple times or not, and the article implies she may have missed some shots, but the way he was crying out, it sounded like she made some hits and he still kept whacking her with the hammer.
https://www.foxnews.com/us/connecticut-man-seen-brutally-attacking-police-officer-hammer-body-camera
I don't know what kind of holster she had, and since she was a detective it likely wasn't a retention-type duty holster. Here's some background for you:
The so-called 21-foot "rule" is an over-simplification of the original Tueller Drill, which was devised by a then-police trainer named Dennis Tueller as a means of teaching rookie street cops that things can go south a lot faster than they might expect. When he had several of his officers run the drill, 21 feet was the average distance within which a [rubber] knife wielding "suspect" could close on an officer and stab him in the chest before the officer could draw from his duty holster and fire a shot.
BUT ... when Tueller devised the drill, departments (his, at least -- IIRC he was with the Salt lake City PD) didn't use level 3 retention holsters. Also, in the drill, the officers
knew the subject was going to react at the signal and try to stab them. They weren't expecting "command voice" to win the day. After his retirement, Tueller gave talks around the country, and he stated flat out that the 21-foot distance was no longer viable, because it takes longer to draw from a level 3 retention holster.
This happened in Connecticut, and I know more than one retired police officer from Connecticut. (One of the local gun shops I check out periodically is run by two retired Connecticut cops). Their police academy puts a lot of emphasis on the use of command voice. I'll go out on a limb and hypothesize that this detective had been taught that command voice would always work, and even though she has made detective she hadn't encountered enough real world scenarios to have learned that t'ain't necessarily so.
So she learned the hard way.
What movie was it in which a character said, "When it's time to shoot, shoot -- don't talk"?
[Edit] Apparently she was working a uniformed patrol shift, so she was probably wearing a duty rig. She obviously was NOT expecting him to attack her, and she was not mentally prepared to shoot when he first charged at her.