What had someone put in Clay's locker days before Hannah took the pills?

Days before Hannah took the pills, someone had placed a note in Clay's locker that contained a list of names of people who had wronged Hannah, including Clay himself. This note served as a catalyst for Clay's feelings of guilt and confusion, as he grAppled with the idea that he might have contributed to her pain. The note highlighted the impact of the actions of others on Hannah's mental state, ultimately leading up to her tragic decision.