Reborn still remembered the gunshots. He remembered what it sounded like when Tsuna died in his arms. He remembered the steadily whitening face and terrified expression of his no-good student when his heart rapidly sped towards its last beat. He remembered the devastated tears of Tsuna's friends when they discovered what he had witnessed.
The second they settled on a time and date for a funeral, Reborn had made plans. He had tracked the murderers down and when the coffin bearers trekked their dejected path down the isle, Reborn made his final stand in a lifeless, gore-soaked room. With nothing but Leon and a tattered suit, Reborn silently removed his worn fedora and held it gently over his heart. He heard the soft footfalls of the second wave of hitmen and when they finally burst into the room with weapons blazing, he met them with a sad smile.
It seemed fitting to die on the day of his student's funeral.