"The events in Sidon were not contained for long. The government began to lose control of the situation in 1975. On the morning of 13 April 1975, PLO Palestinian guerrilla's in a speeding car fired on a church in the Christian East Beirut suburb of Ain El Rummaneh, killing four people, including two Maronite Phalangists. The Church was being opened and thus the presence of the Phalange party was well known at the new church. That same day the situation escalated when a bus carrying armed Palestinians was ambushed by gunmen belonging to the Phalange party. The party claimed that earlier its headquarters had been targeted by unknown gunmen. The attack against the bus in Ain El Rummaneh marked the official beginning of the Lebanese Civil War." Source: Wikipedia