1 Kings 16:15-17

15Zimri began to rule over Israel in the twenty-seventh year of King Asa’s reign in Judah, but his reign in Tirzah lasted only seven days. The army of Israel was then attacking the Philistine town of Gibbethon.

16When they heard that Zimri had committed treason and had assassinated the king, that very day they chose Omri, commander of the army, as the new king of Israel.

17So Omri led the entire army of Israel up from Gibbethon to attack Tirzah, Israel’s capital.