i'm elaine quijano. the pentagon is investigating the apparent murders of three u.s. the afghan army says one of its troops turned his gun on the americans before he was shot dead. the taliban claims this was the gunman and that he was one of their own, an army infiltrator. the attack comes as america's longest war is at another crossroads. the pentagon wants to add thousands of troops to the 8,000-plus already in afghanistan. they're helping in the fight against the taliban, al qaeda and isis. but some in congress want to cut off funding for the 16-year war, saying the u.s. has sacrificed enough blood and treasure. here's tony dokoupil. >> reporter: when an afghan soldier opened fire saturday, killing three americans who were supposed to be his allies. vice president mike pence offered solace at a speech in milwaukee. >> suffice it to say, when heros fall, americans grieve. with the families of these american heroes. >> reporter: after nearly 16 years, more than 2200 casualties and an estimated cost topping $800 billion, the u.s. is deadlocked in its fight with the t