I understand this is a sensitive issue.
I don't know any other way to say it other than that my gut tells me that there was no intent, and I base that on wearing the uniform myself, and being intimately involved with my own daughter's army career.
Intention is 98% of something like this. We can all understand an accident, and we can also understand, but not necessarily be content with, an accident due to negligence. The level of negligence is very important to assigning blame and the hard feelings that come from a fatal incident.
The USA has some cool toys. There have been movies based upon them, like the "Bourne" movies, where the US G. can tell what you ate for dinner and can snoop through written correspondence by satellite. These are all ridiculous. We have capabilities, but they all fall WAY short of what Hollywood insinuates. My point with this is that lack of data, the "fog of war", and the unknown in military operations is very real and hard to describe accurately for those who have not served. When you have troops in contact with whomever, the assumption is automatically made that they are hostiles, and all resources are instantly poured into the fight to resolve it in our favor. Priority #1 is American lives. I know this doesn't sit well with others, but all militaries work this way - they preserve their own first when there is a fight in progress.
In this case, I can only guess what was happening. I'm suspecting that the airmen radio'd "We are taking fire" and at that point, everything goes into returning fire and eliminating the threat. There is no time to analyze in any detail at all, "Who is it?"
In this case, it went on for some time. Once fire is traded, the assumption is "They are enemy, because it is only the enemy who fire on us." Simplistic, but practical, and that's how it's done in the field.
In the mean time, the Pakistani soldiers are taking fire, returning when they can, so the fight continues. The communications chain had to go through two or three levels on both sides, with much confusion as to the location of troops. The articles I have read have said that the two sides said "None of our boys are in grid XYZ; they must be enemy" and unfortunately, the grid/map coordinates were not communicated properly.
I don't know what else to say, other than that I know the mentality of these troops. They are not animals, they are professionals who want to do a difficult job to the best of their ability. Further, the USA is still shedding ROE baggage from Vietnam, where we lost thousands of troops due to the inablity to fight without a hand tied behind their back.
I have to go to dinner, but I'l try and address this all further. Please rest assured the average American is saddened by the deaths of genuinely allied troops. Anyone who is fighting terrorism is considered Brothers in Arms, and the average Pakistani soldier is exactly like the average American soldier; 18 to 22, patriotic, eager to do their duty, and with no desire to harm anybody other than the enemy.