I would have said shaped charge version of the Hellfire rather than a blast frag, HE or MAC (thermobaric) shot if it was a US 'drone strike'. It really does look rather too clean though for my liking. That said, any bets on it being inter-extremist rivalry but blamed on US for ease and deniability? After all, the key extremist group formally known as Al Nusrah Front operate in Idlib, and given that last year they publically 'divorced' from the AQ franchise, why was AQ's 2ic in Idlib on ANF's turf otherwise?