Top Al-Qaeda in the Arabian Peninsula (AQAP) leader Nasir al-Wuhayshi was killed in a US drone strike in Yemen last Friday, but according to US officials the CIA bagged the Al Qaeda leader by pure luck.

According to the officials, the strike went ahead without knowing who the exact targets were, using a “signature strike” technique in which the CIA goes ahead with the drone attack based on patterns of suspected terrorist activity, reported the Washington Post on Wednesday.

Al-Wuhayshi, aside from being the top Al Qaeda leader in Yemen, was the second-in-command overall for global Al Qaeda.

The “signature strike,” in which analysts deconstruct drone footage and other surveillance to detect patterns characteristic of senior Al Qaeda terrorists’ security details, has been controversial to many given that the identity of the targets is unknown.

In some cases the strikes cause collateral damage to civilians and even hostages.

The Obama administration eased guidelines on the strikes after the US-backed government in Yemen fell this year to the Iran-backed Shi’ite Houthi militia.

Apparently the use of “signature strikes” is responsible for the recent uptick in drone operations in Yemen over the last six months, even after joint US-Yemen counter-terror operations on the ground were suspended.

The CIA has refused to comment on al-Wuhayshi’s death, but US officials say there was never a ban on “signature strikes” in Yemen.

In a video that surfaced in April last year, al-Wuhayshi made clear that he’s going after the United States, saying, “We must eliminate the cross. …The bearer of the cross is America!” The video showed what looked like the largest and most dangerous gathering of Al Qaeda in years.

Originally from Yemen, al-Wuhayshi assumed command of AQAP in 2009. He had escaped a Yemeni prison in 2006, and had previously worked as a personal secretary for former Al Qaeda head Osama bin Laden.