BBC reports that the buses in Foua were believed set ablaze by Jabhat Fath al Sham, formerly Al Nusra, the Syrian arm of Al Qaida  Al Nusra was designated a terrorist group by the US, Russia Iran, and eight other countries, so not western supported (officially). But that is not where I rest my argument. JFS has a large arsenal of modern US weapons including TOW anti-tank missiles. How did they acquire and maintain this arsenal? According to the BBC  JFS "remains dominant in Idlib in the north-west of Syria" and that is where most of the anti-Assad forces are concentrated. They are regarded as the most combat effective fighters among the rebel ranks. There is a border between Idlib and Turkey. Weapons have been flowing across aided by the Turks. Qatar has sent supplies to JFS and other Gulf states are suspected. These countries are Western allies and we ship weapons to them. Does that constitute western support for JFS? If not officially, as a matter of practical reality, it does.