Three short lines, and they hold a surprisingly big thought. The speaker begins casually, with "I guess," as if shrugging while talking about something enormous: everyone dies. Nothing new there. The sting comes in the last two lines, where some people simply go "a little earlier than the rest."
That phrase "a little earlier" is a quiet understatement. It makes an early death sound like arriving at a party ahead of everyone else, when it may mean a life cut painfully short. The gap between the light tone and the heavy subject is what gives the poem its force.
The speaker seems resigned rather than angry or panicked. There's acceptance here, maybe a bit of numbness, the kind of calm someone reaches when they've thought about loss and can't argue with it. The mood is plain, subdued and reflective. The poem doesn't offer comfort or an explanation. It just states the fact and lets the silence afterward do the rest of the work.