I've lost consciousness on a few occasions, myself, due to a lack of oxygen to the brain... I know what that, "white light" feels like.

This idea was bandied about when beheading was more common, and it was suspected that the condemned likely were still aware for a few seconds after losing their head. A tale is told of a man who was to be executed , who told his friend to watch his head carefully, after it was cut off. If he was still aware , he would blink his eyes. The friend paid close attention, and sure enough - the eyes blinked !

Could happen ...

Sounds like the whole post-guillotine, head-in-a-basket thing...

Your nervous system may not have shut down, but if you are aware, you cannot be completely dead.

actually there is a scientific reason for the white light.
apparently it has to do with the ions in our brain synapses losing there magnetism & at the very end being released.
i forget exactly but it's something like that.

If you are aware after the fact, you are not really dead yet but you just know you are not gonna make it, you feel yourself dying but then you die I guess... Don’t know how we can really prove if after death for a few seconds we fall into our sub conscious and fully analyze it.