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FILE -- In this Sunday Aug. 5, 2012 file photo, a Pakistani Taliban militant holds a rocket-propelled grenade at the Taliban stronghold of Shawal, in Pakistani tribal region of Waziristan, Pakistan. Pakistani officials said Saturday that it is investigating whether the son of the founder of the powerful Haqqani militant network, Badruddin Haqqani, was killed in a U.S. drone strike this week. The U.S. has long viewed the Haqqani network as one of the biggest threats to U.S. and NATO forces in Afghanistan as well as the country’s long term stability. (AP Photo/ Ishtiaq Mahsud, File)

FILE -- In this Sunday Aug. 5, 2012 file photo, a Pakistani Taliban militant holds a rocket-propelled grenade at the Taliban stronghold of Shawal, in Pakistani tribal region of Waziristan, Pakistan. Pakistani officials said Saturday that it is investigating whether the son of the founder of the powerful Haqqani militant network, Badruddin Haqqani, was killed in a U.S. drone strike this week. The U.S. has long viewed the Haqqani network as one of the biggest threats to U.S. and NATO forces in Afghanistan as well as the country’s long term stability. (AP Photo/ Ishtiaq Mahsud, File)

Afghan attack kills US troops

An Afghan soldier turned his gun on American troops

at a checkpoint in the country's east, killing two Americans and at

least two fellow members of Afghanistan's army in a shooting that marked

both the continuance of a disturbing trend of insider attacks and the 2,000th U.S. troop death in the long-running war. (AP)