They slaughtered the passover lamb, and the priests dashed the blood that they received from them, while the Levites did the skinning.
References for 2 Chronicles 35:11
They set aside the burnt offerings so that they might distribute them according to the groupings of the ancestral houses of the people, to offer to the Lord, as it is written in the book of Moses. And they did the same with the bulls.
They roasted the passover lamb with fire according to the ordinance; and they boiled the holy offerings in pots, in caldrons, and in pans, and carried them quickly to all the people.
Afterward they made preparations for themselves and for the priests, because the priests the descendants of Aaron were occupied in offering the burnt offerings and the fat parts until night; so the Levites made preparations for themselves and for the priests, the descendants of Aaron.
The singers, the descendants of Asaph, were in their place according to the command of David, and Asaph, and Heman, and the king's seer Jeduthun. The gatekeepers were at each gate; they did not need to interrupt their service, for their kindred the Levites made preparations for them.
So all the service of the Lord was prepared that day, to keep the passover and to offer burnt offerings on the altar of the Lord, according to the command of King Josiah.
The people of Israel who were present kept the passover at that time, and the festival of unleavened bread seven days.
No passover like it had been kept in Israel since the days of the prophet Samuel; none of the kings of Israel had kept such a passover as was kept by Josiah, by the priests and the Levites, by all Judah and Israel who were present, and by the inhabitants of Jerusalem.
In the eighteenth year of the reign of Josiah this passover was kept.
After all this, when Josiah had set the temple in order, King Neco of Egypt went up to fight at Carchemish on the Euphrates, and Josiah went out against him.
But Neco sent envoys to him, saying, "What have I to do with you, king of Judah? I am not coming against you today, but against the house with which I am at war; and God has commanded me to hurry. Cease opposing God, who is with me, so that he will not destroy you."
References for 2 Chronicles 35:21