What does this poem mean? is it even a poem?

Clearly it's a poem, and about inward, invisible heartbreak, frequent because of the heart's fragility. I'm not sure, though, what you mean by the line "one shot and a kill". It may mean that the heart feels as if it had been shot and killed, but if so, you need to say that more clearly. If you meant something else, you need to say whatever that is more clearly.