2 Chronicles (Author Compiled by Isaiah and Ezra from records of Nathan, Gad, Iddo, Ahijah, Jehu and others.)
Chapter 21
4And Jehoram established himself over the kingdom of his father, and strengthened himself; and he slew all his brethren with the sword, and certain also of the princes of Israel.
Original from The Bible Foundation - bf.org. They claim public domain status for their original text.