Why does this happen during death?

I worked on ambulance crews during college and have also been present when friends and family have died. No disrespect intended, but I have no idea what you are talking about, especially considering absolutely everything breathed into or out of a person must pass through their throat.

There are pronounced and dramatic changes in the way a person breathes, as death approaches and there are often one or more "last gasps," sometimes called a "death rattle." Basically air, sputum, vomit and sometimes blood are the only substances involved in dying.

Also urine and feces, but usually not around the throat.

That's asphyxiation, usually accompanied by severe muscle spasms. It happens when the lungs fill with fluid, you see it when someone has been shot or in crushing or blast injuries where a broken rib has perforated the lung.

It's not the soul exiting the body, if that's what you're wondering.

Actual medical death is when electrical activity is the higher areas of the brain stops.

Loool wow spasms from blood loss, damaged nerves etc.

Damn Christians are clueless about science.

It doesn't. I was with my father and mother when they died and neither of them did anything like that.

Let me kill you and you can find out for yourself.

they were probably just heavy smokers.