Four short lines carry a surprisingly heavy idea. The poem begins with a plain fact: people die. It then gives two ages, 23 and 89, one young and one old, as if to say death doesn't keep to any schedule. So far, nothing unusual. We expect a poem about mortality to remind us that life can end early or late.
The last line is where the poem turns. "Some while living" suggests that a person can perish without dying, that someone might go numb, give up, or lose themselves while their heart still beats. The speaker doesn't say why this happens, and the poem is stronger for leaving it open.
The tone is calm and matter-of-fact, almost cold, which makes the final line land harder. The white space around that line adds to the effect, leaving a quiet, unsettling pause. The mood is sober and a little haunting, and it nudges the reader to ask what it means to be truly alive.