How to make a grabpass only grab 1 frame instead of continuous frames?

Trying to make a sort of time-stop effect using a shader.

Currently the grabpass will keep taking frames. I want it to only take the first frame it sees and then keep sending that one frame. Or send that first frame to a different shader if it has to / if it can; anything to grab the first frame of the grabpass so that I can then use that for whatever other shader/effect I want to apply afterward.

I've searched everywhere for this for the past week or so but the closest I get is a camera that renders to a flat plane, which is no good.

Again, ANY way to make it only grab 1 frame, or have it stop grabbing frames after a period, or make it reuse a certain frame repeatedly, or a way to save a frame as a texture and reuse that over and over, etc.

 

You don't want a grab pass then. Have your camera render to a texture and pass that to your material.

 

So is there is no way to access any one of the frames from the grabpass repeatedly or at a later moment?