The streets of Beirut filled with cars fleeing the city as soon as news spread that one of Lebanon's most prominent Christian politicians, Pierre Gemayel, had been assassinated in the capital. The killing of his uncle, President Bashir Gemayel, in 1982, marked the beginning of a particularly bloody chapter in Lebanon's 15-year Civil War. And the fear now spreading through the country is that this latest attack could usher in a similar period of heightened violence.Pierre Gemayel, the son and nephew of former presidents, had been the Minister of Industry in the fragile anti-Syrian ruling coalition led by Prime Minister Fouad Siniora. That government was already on the verge of collapse, following the resignation last week of all the Shi'ite ministers in his cabinet after Hizballah accused Siniora and his allies of collaborating with the United States and Israel in this summer's war.Hizballah and the pro-Syrian opposition have promised mass demonstrations and strikes, perhaps as early as Thursday, to press their demand for the government's resignation and replacement by a cabinet in which they have greater representation. The government's supporters have promised counter demonstrations. Now, the death of Gemayel raises the prospect of a confrontation between the two sides. Already, supporters of Gemayel have rioted in the streets around the hospital that contains his remains.With more mayhem likely, local suspicion for Gemayel's murder falls on those who would most benefit from instability in Lebanon. Siniora's allies blame Syria, whom they also accuse of assassinating former Prime Minister Rafik Hariri in February 2005. Since Hariri's death, a bombing campaign has killed or injured a series of anti-Syrian politicians and journalists. The last murder, of newspaper publisher Gebran Tueni, took place in December of last year.But it is unlikely that any of these killings could have taken place without at least the assistance of some parties or factions within Lebanon. Many of the killings have been sophisticated, well-timed operations that bear the hallmarks of a highly trained intelligence organization. Several former leaders of Lebanon's own police and security services are in prison in this country under suspicion for involvement in the Hariri assassination. Hizballah, which itself has this kind of operational capability, has accused Israel of staging these assassinations to sow disunity.While the identity of Gemayel's killers remains a matter of speculation, what is clear is that the stakes are getting higher for Siniora. By tradition, the Lebanese cabinet contains members of all the country's main sectarian groupings. Without any ministers who are Shi'ite — Lebanon's largest community — the legitimacy of his government is open to question. And if the government can't maintain security — or even protect its own officials — many Lebanese may turn to someone who can.