And as Josiah turned himself, he spied the sepulchres that were there in the mount, and sent, and took the bones out of the sepulchres, and burned them upon the altar, and polluted it, according to the word of the LORD which the man of God proclaimed, who proclaimed these words.
When Josiah looked around, he saw the tombs on the mountain and ordered them to be opened. He took out the bones and burned them on the altar, just as the LORD had said through the prophet's message. This made the altar impure.