In April 1975, four persons, among them two men close to the Gemayel family, were killed during an attack on a church inauguration ceremony by unknown attackers in the Beirut suburb of Ain al-Roummaneh. In retaliation Phalangist militias killed 28 passengers of a bus later that day, most of them Palestinian with some that were deemed to be armed that were coming back from a rally at camp Tel el-Zaatar, since they suspected Palestinians to be behind the church attack. The Bus Massacre is commonly considered as the spark that set off the Lebanese Civil War. In the following days, the 8,000-strong party militia, the Kataeb Regulatory Forces, together with its allies, the Tigers militia, Al-Tanzim, Marada Brigade, Guardians of the Cedars, Lebanese Youth Movement, Tyous Team of Commandos and other formations, was heavily engaged in street fights against the Palestinian militias and their allies in the anti-government secular Lebanese National Movement.