In my opine, you(as a armed citizen or license holder) can use a firearm(deadly force) if a violent attacker uses a blunt object or EDW(electric discharge weapon) or if they start to beat/hit you.
Around 4 years ago, a uniformed armed female deputy was attacked & beaten by a larger unarmed subject who fled a Home Depot in a dispute. The thug pounded the deputy's head into the pavement then ran off.
She was in a ICU and almost died.
In a more recent event, 2 young women were attacked by a well dressed man with a baseball bat.
The video is on Youtube.com .
I urge any use of force instructor or tactics trainer to review the clip & share it with their students or cadets. It shows how a sudden or violent assault can occur nearly anywhere.