1 Kings 16:15–20 (ESV)

15 In the twenty-seventh year of Asa king of Judah, Zimri reigned seven days in Tirzah. Now the troops were encamped against Gibbethon, which belonged to the Philistines,

It must have been a monstrous week in Tirzah. Zimri became king by killing Elah; he wiped out the family and friends of Baasha and Elah within a week, leaving no one alive; and when that news reached the besiegers of Gibbethon, the soldiers proclaimed their commander-in-chief, Omri, as king. He immediately moved the siege to Tirzah, the capital, and Zimri soon understood that it was an unequal battle and killed himself.

Here we hear the damning judgment again. Zimri doing evil in the sight of the Lord, walking in the way of Jeroboam (who was king about thirty years earlier). He too—in the seven days that he was king—set a bad example to the people—a mortal sin for a king.