In the twenty-sixth year of Judah's King Asa, Elah son of Baasha became king over Israel in Tirzah; [he reigned] two years.
References for 1 Kings 16:8
His servant Zimri, commander of half his chariots, conspired against him while Elah was in Tirzah drinking himself drunk in the house of Arza, who was in charge of the household at Tirzah.
In the twenty-seventh year of Judah's King Asa, Zimri went in, struck Elah down, and killed him. Then Zimri became king in his place.
When he became king, as soon as he was seated on his throne, Zimri struck down the entire house of Baasha. He did not leave him a single male, whether of his kinsmen or his friends.
References for 1 Kings 16:11
So Zimri exterminated the entire house of Baasha, according to the word of the Lord He had spoken against Baasha through Jehu the prophet,
References for 1 Kings 16:12
because of all the sins of Baasha and the sins of his son Elah, which they committed and caused Israel to commit, provoking the Lord God of Israel with their worthless idols.
The rest of the events of Elah's [reign], along with all his accomplishments, are written about in the Historical Record of Israel's Kings.