Some maybe not needed details,but for those who do not know i need to say that death can be dirty thing, especially violent death.
Right after the death occurs muscles relax, including anal sphincter, so very often there s gonna be feces.
In violent death organs may (very often) prolapse of of the body, and body fluids may be everywhere, so it adds to the speed of decomposition and smell.

Multiply that with some number of body (in case of some big SHTF event) and you may get the picture.

It is very very dirty and smelly. Rats, flies, dogs, other animals and insects. It is bad picture.

It is not like dying in home with full care or in hospital, even there it can be dirty. It is one more thing that is not like in the movies.

I remember the cases where I simply could not enter the room, where was body few days old, with billions of flies, on hot air, and I have pretty good stomach for that things.