The room is silent and still except for that of the buzzing of the ordinary fly. The poem describes a quiet period between "heaves," suggesting disturbance proceeded this moment and that more cataclysms will follow. This shows a moment of expectation, and that of waiting. The stillness still fills the air and the watchers gathered around the speaker are silent. And still the only sound is the fly's buzzing. Here we find some kind of inner peace with the speaker; because the tone remains calm and the speaker’s sequence of events are short and factual.
The people witnessing the speaker have exhausted their grief (their eyes are "wrung dry" of tears); which show that this site was bound to happen and they were fully aware of the inevitable. The speaker’s breathing indicates that "that last onset" or death is about to happen. When “last onset” is defined in Christian terms, "last" means an end and “onset” means beginning. Death is the beginning of eternal life for Christians. So was the speaker referring to the