2 Chronicles 23
Revolt against Athaliah 1
In the seventh year of Athaliah's reign, Jehoiada the priest decided to act. He summoned his courage and made a pact with five army commanders: Azariah son of Jeroham, Ishmael son of Jehohanan, Azariah son of Obed, Maaseiah son of Adaiah, and Elishaphat son of Zicri.
These men traveled secretly throughout Judah and summoned the Levites and clan leaders in all the towns to come to Jerusalem.
They all gathered at the Temple of God, where they made a solemn pact with Joash, the young king.
Jehoiada said to them, "Here is the king's son! The time has come for him to reign! The LORD has promised that a descendant of David will be our king.
This is what you must do. When you priests and Levites come on duty on the Sabbath, a third of you will serve as gatekeepers.
Another third will go over to the royal palace, and the final third will be at the Foundation Gate. Everyone else should stay in the courtyards of the LORD's Temple.
Remember, only the priests and Levites on duty may enter the Temple of the LORD, for they are set apart as holy. The rest of the people must obey the LORD's instructions and stay outside.
You Levites, form a bodyguard around the king and keep your weapons in hand. Kill anyone who tries to enter the Temple. Stay with the king wherever he goes."
So the Levites and all the people of Judah did everything as Jehoiada the priest ordered. The commanders took charge of the men reporting for duty that Sabbath, as well as those who were going off duty. Jehoiada the priest did not let anyone go home after their shift ended.
Then Jehoiada supplied the commanders with the spears and the large and small shields that had once belonged to King David and were stored in the Temple of God.
He stationed all the people around the king, with their weapons ready. They formed a line from the south side of the Temple around to the north side and all around the altar.
Then Jehoiada and his sons brought out Joash, the king's son, placed the crown on his head, and presented him with a copy of God's laws. 
They anointed him and proclaimed him king, and everyone shouted, "Long live the king!"
The Death of Athaliah 12
When Athaliah heard the noise of the people running and the shouts of praise to the king, she hurried to the LORD's Temple to see what was happening.
When she arrived, she saw the newly crowned king standing in his place of authority by the pillar at the Temple entrance. The commanders and trumpeters were surrounding him, and people from all over the land were rejoicing and blowing trumpets. Singers with musical instruments were leading the people in a great celebration. When Athaliah saw all this, she tore her clothes in despair and shouted, "Treason! Treason!"
Then Jehoiada the priest ordered the commanders who were in charge of the troops, "Take her to the soldiers in front of the Temple, 
and kill anyone who tries to rescue her." For the priest had said, "She must not be killed in the Temple of the LORD."
So they seized her and led her out to the entrance of the Horse Gate on the palace grounds, and they killed her there.
Jehoiada's Religious Reforms 16
Then Jehoiada made a covenant between himself and the king and the people that they would be the LORD's people.
And all the people went over to the temple of Baal and tore it down. They demolished the altars and smashed the idols, and they killed Mattan the priest of Baal in front of the altars.
Jehoiada now put the priests and Levites in charge of the Temple of the LORD, following all the directions given by David. He also commanded them to present burnt offerings to the LORD, as prescribed by the Law of Moses, and to sing and rejoice as David had instructed.
He also stationed gatekeepers at the gates of the LORD's Temple to keep out those who for any reason were ceremonially unclean.
Then the commanders, nobles, rulers, and all the people of the land escorted the king from the Temple of the LORD. They went through the upper gate and into the palace, and they seated the king on the royal throne.
So all the people of the land rejoiced, and the city was peaceful because Athaliah had been killed.