senior al-Qaeda commander killed in Syria (?)

Rebel troops say that a senior al-Qaeda member was killed in a suicide bomb attack in the town of Allepo. There was no immediate claim on who did the bombing or who he/she was working for. However, the rebels quickly accused the Islamic state. Could have this been an accident? If it was a commander, it couldn't be accidental. Yet, what if the commander hired the suicide bomber. There is no other information about the person that did it, but whoever did, it's safe to say we are one step closer to ending the war against al Qaeda.