That's the key.
If he had chosen taser and it didn't work she might (as slow as her fat ass was) close the distance before he could draw.
Two cops on the scene where one tries a taser and the other has deadly drawn and ready ... maybe. But it's not the kind of Cagney and Lacey shit to just be making up for the first time in the real.
Y'all should take your ideas to the local police academy and see if they'll let up you run it as a training scenario with you as a role-player.
It's a matter of the right tools, training and preparation for the job.
The police are not what you should be using for social services.
The police are not what you should be using for mental health episodes.
But nobody seems to want to actually spend the time and money to have folks trained and equipped and ready on standby to deal with mental illness.
If you have the correct tools for the job on hand and ready to be deployed, most uses of deadly force could be avoided in mental illness situations.
Capture shields
Net launchers
Non-lethal mass impact devices
Water cannons
Tranquilizer guns
Air blast devices
The list goes on.
BUT none of it works unless folks have the items, are trained to use the items and have a plan to use them first and use them effectively.
If all you pay for is some lone guy with a gun, a badge and a bad attitude, well the mentally ill person doesn't care about the badge and the bad attitude and you can't fault the police for defending their lives the same way any citizen would have the right to.
You Could train the police to do all that, but nobody seems to want that, especially not the police who if you listen to the media, you get the idea that somehow they hate the idea of being something other than Judge Dredd. I'll bet the police unions would be all crazy mad about telling officers they can't just kill folks.
Not to mention the stupid greedy cities don't want to pay for the training and equipment that would need to be provided.
It would mean you need to pay for teams of police not just 1 driving around. It would mean you would need to pay for all the equipment to be with them and ready for deployment.
The cities and the taxpayers would need to start having to pay out huge sums of money before they will be willing to invest in such changes.
The police would need to get this vile "immunity" B.S. removed before they are willing to learn and train for non-lethal takedowns.
Also you might need a slight tweaking of the laws to say well, you were doing something the average citizen would have been fine with killing you for to stop you from killing them, so if you got a bit banged up in the process of being non-lethally stopped, we are going to slam the door in the face of your ambulance chasing lawyers...
For those that think it's impossible, try this exercise:
You are stuck in North Korea
Fat man's mentally ill son is running around rampaging with knives in both hands.
Your orders are to get him back to his padded room.
If you kill him, you and your entire family for 3 generations are sent to the liquidation camps, and fed to the dogs or otherwise dispatched.
If you fail and he hurts a bunch of folks, it causes great embarrassment to Dear Leader, and you and your family for 3 generations are sent to the labour camps.
Now that your life and the lives of your family are on the line, come up with a plan to get Dear Leader's son disarmed safely, and back in his padded room without injuring him too badly. Figure out what equipment you want to bring with you, how many folks, and what your tactics are.
I'll bet you could figure it out & have a good chance of success.
(If you need clues, I could point you to some old Japanese movies showing an idea or two on capturing folks armed with swords).