Shallum son of Jabesh began to rule over Israel in the thirty-ninth year of King Uzziah's reign in Judah. Shallum reigned in Samaria only one month.
Then Menahem son of Gadi went to Samaria from Tirzah and assassinated him, and he became the next king.
The rest of the events in Shallum's reign, including his conspiracy, are recorded in The Book of the History of the Kings of Israel.
At that time Menahem destroyed the town of Tappuah and all the surrounding countryside as far as Tirzah, because its citizens refused to surrender the town. He killed the entire population and ripped open the pregnant women.
References for 2 Kings 15:16