From Aish.com:
In 2003, an Arab terrorist blew himself up on the #2 bus en route from the Western Wall in Jerusalem, killing 23 people and wounding 136, many of them children. The attack occurred on a double-length bus crowded with families on a summer vacation outing, and became known as the “family massacre.” The bomber, from a Hamas cell in Hebron, was apparently disguised as an Orthodox Jew. Following the attack, the Israeli government decided to wage an all-out war against Hamas and other terrorist elements, and to freeze the diplomatic process with the Palestinian Authority.