`  == Parked text from opening of Responsibility section  ==  There was considerable confusion after the attack about the motivations of the attacker and the source of its support. It was not clear whether conflicting claims of responsibility indicated that Pakistani Taliban, Afghan Taliban, and al-Qaeda were working independently from each other. U.S. officials said that their investigators have yet to determine which of the groups organized the attack.   A video released in the days after the attack featured the purported bomber stating that he was carrying out the attack in response to the death of Baitullah Mehsud, the Pakistani Taliban leader who was killed by a U.S. drone in August earlier that year. The CIA launched more than 50 drone attacks in 2009, compared to more than 30 in 2008, according to an ABC News tally. The CIA officials based at Forward Operating Base Chapman were at the center of the drone campaign, according to intelligence officials, and they were looking for informants to help them find senior al-Qaeda and Haqqani leaders.`