He died from a debilitating illness. Leorio feels deeply remorseful about being unable to save his friend, as the illness was entirely curable, but required a surgery he could not afford. Thus, he aspires to become a doctor and takes part in the 287th Hunter Examination.
- Pietro is his name in the 1999 anime adaptation. In the manga, it has never been mentioned.
- Both Leorio and Pietro are adults during the latter's death, implying that Leorio's dream of becoming a doctor is a fairly recent one, though this differs in the 2011 anime.