Boy found the apparitions in the tunnel weird because the girl was supposed to be the
only one who died that night, so he experimented and found that rumors strengthened the apparition. He weakened the rumors by censoring and reporting them, blurring the apparitions.
Streisand effect happened and the rumors only strengthened, revealing that he knew only the girl died that night because
he was the murderer. He was trying to weaken the rumors bc the apparition would reveal his face.