The attack itself was disturbing enough. As an Israeli bus approached Emmanuel, a Jewish settlement in the West Bank, a band of Palestinian guerrillas detonated two roadside bombs. When passengers fled the stricken vehicle, the militants gunned them down and flung grenades in their direction. Ten civilians were killed in the assault, and 30 were injured.
Then came the added horror. It was not just the usual suspect, the radical Islamic group Hamas, that took responsibility for the outrage. Also claiming a part was the Aqsa Martyrs Brigade, an underground militia associated with Yasser Arafat. That would be the same...