“Now the rest of the acts of King Josiah, and all that he did, are they not written in the Book of the Annals of the Kings of Judah? In his days Pharaoh Neco king of Egypt went up to the king of Assyria to the Euphrates River. King Josiah went to meet him. But when Pharaoh Neco saw him at Megiddo, he killed him. His servants carried him dead in a chariot from Megiddo. They brought him to Jerusalem. They buried him in his own tomb. The people of the land took Jehoahaz son of King Josiah, anointed him, and made him king in place of his father.”
Once again for more information about King Josiah, you can check out the lost “Book of the Annals. Apparently, there was fight with Egypt as King Neco met King Josiah at Megiddo, in the upper Manasseh territory and killed him there. King Neco of Egypt was probably King Nekau II (610-594 BCE). As the Assyrian empire was falling apart he took a lot of land from Assyria. He had a battle at Megiddo with the Assyrians and King Josiah, where Josiah was killed. It seems that Judah and King Josiah sided with the Assyrians. They took his body back to Jerusalem and buried it in a separate tomb. Then his son King Jehoahaz took over as the king of Judah.