When Josiah turned around, he noticed tombs up on the hillside. So he ordered the bones to be taken out of the tombs. He then burned them on the altar, desecrating it. (This was in agreement with the word that the LORD announced by the man of God when Jeroboam stood by the altar at the festival.) Josiah then turned and saw the tomb of the man of God who had predicted these things.
References for 2 Kings 23:16
"What's this gravestone I see?" Josiah asked. The people of the city replied, "That tomb belongs to the man of God who came from Judah and announced what you would do to the altar of Bethel."
"Let it be," Josiah said. "No one should disturb his bones." So they left his bones untouched, along with the bones of the prophet who came from Samaria.