According to Tigerlikesrooster (I don't command usage of the Korean language) the girls were supposedly formenting a rebellion amongst ethnic Tibetans, but according to the sign on the girls neck, she was guilty of murder.
As for the blindfolds and the ditch...well, that's China for you.
I agree, I would like to know more information about the situation, but I doubt that will ever come to light.
It is a very strange situation but just to be on the safe side it can't hurt to buy American if you can find anything made in America anymore. Maybe someone on FR will compile a list of American companies to make things easier. I would definitely use it.
The presence of these personnel in such numbers implies that whatever she and the others were accused of, it was not merely a criminal act, and was justice wasn't the intent of the punishment. This scene is political.