Nightly News | September 23, 2012
>>> the growing instances of afghan troops and police turning their guns on their american partners has not only threatened to undermine the american mission here, it is also only added more worry and pain back home for those who now see their loved ones threatened from inside and out. before leaving the states, i spent time with one family left both anguished and angry by the manner in which their son died. when their son shipped out to war, like many parents, deep down, the buckleys feared it could end with a knock at the door and those excruciating words no one forgets.
>> i'm sorry to inform you that your son, lance corporal buckley passed away. yesterday in afghanistan.
>> lance corporal greg buckley jr. was killed just days before he was supposed to come home. the 21-year-old and two fellow marines were shot to death while working out in a gym. the military calls them green on blue, or insider attacks. mr. buckley has his own word.
>> it was an execution.
>> since the start of the year, at least 51 american and allied troops have been killed in insider attacks, at first written off mostly because of personal grudges, in recent weeks, the military has come to realize a dangerous pattern and has hit the pause button on many afghan-u.s. operations. who are you angry at?
>> the government, they dropped the ball.
>> that's because greg buckley says they should have done more to protect his son from afghan training partners who were becoming increasinge e.
>> dear, mom, dad.
>> his mother still clings to the words of one of greg 's last letters homes.
>> you know i love you more than any person.
>> a letter which eerily sounds like a good bbygoodbye.
>> you'll always be my mother and the queen of everything. i don't know how to go on with my life without him.
>> the buckleys wall is still covered by tributes left by neighbors and strangers. and at a recent high school football game, the city became one of the many american cities to honor their fallen.
>> my son is asking me to speak out. he doesn't want to see anymore kids die the way he died.
>> reporter: his dad admits he was against his son joining the marines but is immensely proud of him. but he wasn't sure that greg fully understood the cost of war. but this was a price that no one was prepared to paid.
>> anything that happened on that battlefield, i could accept it. i would be heart broken.
>> since the start of the year, more than 50 afghans have been killed by fellow afghan security force members. we'll