Hand on throat means one thing: asphyxia. It happens rather quickly. Try holding your breath.

As soon as someone like that stepped in I would go to a defensive posture with my hand discreetly on my weapon under my shirt.

If he did grab me by the throat and one or two immediate blows with my free hand did not break him loose, I would be in fear for my life and would shoot him as many times as necessary to stop the attack.