Reuters said that if the gunman turns out to have been an Afghan security guard for coalition troops, it would be the ninth insider attack this year bring the death toll of foreign personnel to 14.
That is down dramatically from last year, when a spate of so-called insider attacks prompted NATO to curtail some joint operations with Afghan government forces.
That's not very reassuring.
Identifying the "good guys" in Afghanistan is problematic to say the least. We've built them a military that their government can not support without huge amounts of western money and is infiltrated at every level by people who are either our sworn enemies or will change sides at a moments notice.