The tip-off which enabled two Hellfire missiles fired by US drones to locate and kill the US-born Anwar al-Awkali reached US intelligence as a result of a power struggle within Al Qaeda's leadership in Yemen. Killed too was a second US-born al Qaeda operative.DEBKAfile's counter-terror sources disclose that the internal strife was sharpened by the recent arrival in Yemen of the new Al Qaeda leader Ayman Zuwahiri, who determined to purge AQAP ranks of its American element ahead of his next plans.