There are two competing theories in Beirut for who killed Pierre Gemayel. They reflect Lebanon's deep divide since Syrian forces withdrew amid popular demonstrations after the assassination of former president Rafik Hariri in February last year.
The US-backed government and its supporters accuse Syria and, in some cases, its ally Hezbollah.
They say Syria wants to wreck an international tribunal to try those accused of killing Hariri. A UN report links Lebanese and Syrian security services to the Lebanese prime minister's death, but Damascus denies involvement.
The theory suggests that, after six Cabinet ministers resigned this month and the killing, Syria's agents in Lebanon need kill only two more and they will achieve a collapse of the government, because it will be constitutionally inquorate. A fresh government will block the tribunal, and Damascus will avoid the embarrassment of standing trial over Hariri.
Other related theories suggest rogue elements in Syrian security acting outside President Bashar al-Assad's knowledge, seeking to intimidate Lebanese members of parliament in the run-up to ratification of the UN tribunal.
The other main theory accuses the US or its allies in Lebanon of killing Gemayel to stop the opposition, led by Hezbollah, from bringing down the government and curtailing US influence. It also suggests an attempt to isolate Syria once again, just as the West wants to re-engage Damascus over possible help in Iraq.
Proponents of this theory believe the killing only makes it harder for Lebanese opponents of the tribunal in its current form to vote against, for fear of being associated with a pro-Syrian agenda.
"If anything this assassination has expedited the decision in the UN to pass the resolution," said Ghorayeb, referring to UN Security Council members Russia and Qatar, who had reservations, but came on board hours after Gemayel's killing.