What does the poem "I heard a fly buzz" mean about death?

Consider the forms of life that the speaker identifies in the poem:  herself, a king, and the lowly fly. 

The speaker, as she listens to the vibrant buzz of the lowliest creature on earth, the fly, cannot help but feel envious of its claim to the living world.  The fly, a common parasite on corpses, may also be a vulture-like symbol.  It waits for her to die so it can continue its own life.

The King, mentioned in line 7, may well be Christ the King, who has the only power over death.  However, the poem does not seem very hopeful.   The death seems lonely and alone, the fate that will meet all of us someday.   Death is the only thing we do alone.

(Cheerful, huh?) 

Here is the text of the poem:

I heard a fly buzz when I died;
The stillness round my form
Was like the stillness in the air
Between the heaves of storm.

The eyes beside had wrung them dry,
And breaths were gathering sure
For that last onset, when the king
Be witnessed in his power.

I willed my keepsakes, signed away
What portion of me I
Could make assignable, and then
There interposed a fly,

With blue, uncertain, stumbling buzz,
Between the light and me;
And then the windows failed, and then
I could not see to see.